Hole transport compositions and related devices and methods (i)

ABSTRACT

A composition comprising: at least one compound comprising a hole transporting core, wherein the core is covalently bonded to a first arylamine group and also covalently bonded to a second arylamine group different from the first, and wherein the compound is covalently bonded to at least one intractability group, wherein the intractability group is covalently bonded to the hole transporting core, the first arylamine group, the second arylamine group, or a combination thereof, and wherein the compound has a molecular weight of about 5,000 g/mole or less. Blended mixtures of arylamine compounds, including fluorene core compounds, can provide good film formation and stability when coated onto hole injection layers. Solution processing of OLEDs is a particularly important application.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional application61/361,147 filed Jul. 2, 2010 and also to U.S. Provisional application61/448,579 filed Mar. 2, 2011, and each of these disclosures areincorporated herein by reference in its entirety.

BACKGROUND

A need exists to provide better organic light emitting devices (OLEDs)including better materials used in the devices. In particular, betterOLED devices and materials, including hole transporting materials(HTMs), are needed. An OLED operation is based on injection, transportand recombination of two types of charge carriers: holes and electrons.It is important in an OLED device to control the injection and transportof these two types of carriers so as to enable the recombination tooccur in the EML where the luminescent species are located. The locationwhere these species meet and recombine can dictate the efficiency andlifetime of the device. Vapor processed OLED devices can adopt amultilayer strategy of using complex device architecture of 6-8 layersat times to effectively control and alter the charge carrier flow asneeded to optimize performance. However, for solution processed devices,it can be more challenging to form multilayer structures as the solventfor a given layer can re-dissolve the previously applied layer. Thevapor approach gives good performance and has seen some adoption in theindustry, but solution processing holds the promise of significantlyhigher throughput and lower costs and, because of that, is of greatcommercial promise.

In particular, a need exists for a good platform system to controlproperties of hole injection and transport layers such as solubility,thermal stability, and electronic energy levels such as HOMO and LUMO,so that the materials can be adapted for different applications and tofunction with different materials such as light emitting layers,photoactive layers, and electrodes. In particular, good solubility andintractability properties are important. The ability to formulate thesystem for a particular application and provide the required balance ofproperties are also important.

Additional background material can be found in, for example, (a) Chargecarrier transporting molecular materials and their applications indevices, Shirota, et al., Chem. Rev., 2007, 107, 953-1010, (b) Organicelectroluminescent diodes, Tang, et al., Appl. Phys. Lett. 1987, 51,913-915.

SUMMARY

Embodiments described herein include, for example, compositions,devices, methods of making compositions and devices, methods of usingcompositions and devices, and kits. Compositions can be reactivecompositions, ink compositions, solid or liquid compositions, andcompositions formed after a reaction step, including a crosslinking,oligomerization, or polymerization step.

One embodiment provides a composition comprising: at least one firstcompound and at least one second compound different from the first,wherein the at least one first compound comprises a hole transportingcore which is a fluorene core, wherein the hole transporting core iscovalently bonded to a first arylamine group and also covalently bondedto a second arylamine group, and wherein the core is further covalentlybonded to at least two solubilizing groups comprising at least fourcarbon atoms, and wherein the solubilizing groups are optionallysubstituted with intractability groups; wherein the at least one secondcompound comprises a hole transporting core which is a fluorene core,wherein the hole transporting core is covalently bonded to a firstarylamine group and also covalently bonded to a second arylamine group,wherein the second compound further comprises at least oneintractability group which may be bonded to the first arylamine group,the second arylamine group, or both; and wherein the first and secondcompounds have molecular weight of about 5,000 g/mole or less.

In one embodiment, the relative amounts of the first and secondcompounds are about 99:1 to about 1:99 by weight, respectively. In oneembodiment, the relative amounts of the first and second compounds areabout 90:1 to about 10:90 by weight, respectively. In one embodiment,the relative amounts of the first and second compounds are about 20:80to about 40:60 by weight, respectively. In one embodiment, the relativeamounts of the first and second compounds are about 99:1 to about 80:20by weight, respectively. In one embodiment, the relative amounts of thefirst and second compounds are about 40:60 to about 60:40 by weight,respectively. In one embodiment, the molecular weight of the firstcompound is about 2,000 or less, and the molecular weight of the secondcompound is about 2,000 or less. In one embodiment, the molecular weightof the first compound is about 1,000 or less, and the molecular weightof the second compound is about 1,000 or less.

In one embodiment, the first compound has only two arylamine groups, andthe second compound has only two arylamine groups. In one embodiment,the core fluorene group of the first and second compounds are bonded tothe arylamines at the 2 and 7 positions of the fluorene group and thecore fluorene group is bonded to the solubilizing groups at the 9position. In one embodiment, for the first compound the two solubilizinggroups each comprise at least eight carbon atoms. In one embodiment, thesecond compound comprises at least one intractability group which isbonded to the first arylamine group, and at least one intractabilitygroup which is bonded to the second arylamine group.

In one embodiment, the intractability group for the second compound isvinyl. In one embodiment, the intractability group for the secondcompound is vinyl which is covalently bonded to a phenyl ring to form astyrene unit. In one embodiment, for the first and second compounds, thefirst and send arylamine groups are the same group. In one embodiment,the two solubilizing groups bonded to the fluorene core are the samegroups.

In one embodiment, at least one of the arylamine groups comprises anoptionally substituted naphthyl group bonded to nitrogen. In oneembodiment, at least one of the arylamine groups comprises an both anoptionally substituted naphthyl group and an optionally substitutedphenyl group bonded to nitrogen. In one embodiment, the first and secondcompounds have a solubility of at least 5 wt. %. In one embodiment, theintractable groups are polymerizable groups.

In one embodiment, for the first compound, the solubilizing group issubstituted with the intractability group, and for the second compoundthe core further comprises at least two solublizing groups comprising atleast four carbon atoms. In one embodiment, the relative amounts of thefirst and second compounds are about 20:80 to about 40:60 by weight,respectively. In one embodiment, the relative amounts of the first andsecond compounds are about 25:75 to about 35:65 by weight, respectively.In one embodiment, for the first compound the intractability group isbenzocyclobutane. In one embodiment, for the second compound the corefurther comprises at least two solublizing groups comprising at leasteight carbon atoms. In one embodiment, for the second compound thesolubilizing groups do not comprise intractability groups. In oneembodiment, the first compound and the second compound comprisedifferent intractability groups. In one embodiment, the first compoundis represented by:

In one embodiment, the second compound is represented by:

In one embodiment, the first compound is represented by

and the second compound is represented by:

In one embodiment, for the first compound, the solubilizing group of thecore is unsubstituted with intractability group. In one embodiment, therelative amounts of the first and second compounds are about 99:1 toabout 80:20 by weight, respectively. In one embodiment, the relativeamounts of the first and second compounds are about 95:5 to about 85:15by weight, respectively. In one embodiment, for the first compound theintractability group is on at least one of the arylamine groups and isvinyl. In one embodiment, for the second compound the core furthercomprises to groups bonded to fluorene which are C3, C2, or C1 groups.In one embodiment, for the second compound intractability groups bondedto the first and second arylamine which are vinyl bonded to phenyl toform a para-styrene. In one embodiment, the first compound does notcomprise intractability groups bonded to the core. In one embodiment,the first compound is represented by:

In one embodiment, the second compound is represented by:

In one embodiment, the first compound is represented by:

and the second compound is represented by:

In one embodiment, for the first compound, the solublizing group issubstituted with the intractability group and the for the secondcompound, the core does not comprise at least two solublizing groupscomprising at least four carbon atoms. In one embodiment, the relativeamounts of the first and second compounds are about 80:20 to about 20:80by weight, respectively. In one embodiment, the relative amounts of thefirst and second compounds are about 60:40 to about 40:60 by weight,respectively. In one embodiment, for the first compound theintractability group is vinyl. In one embodiment, for the first compoundthe intractability group is vinyl bonded to a phenyl to form a styreneunit. In one embodiment, for the second compound the core furthercomprises to groups bonded to fluorene which are C3, C2, or C1 groups.In one embodiment, for the second compound intractability groups bondedto the first and second arylamine which are vinyl bonded to phenyl toform a para-styrene. In one embodiment, the first compound isrepresented by:

In one embodiment, the second compound is represented by:

In one embodiment, the first compound is represented by:

and the second compound is represented by:

In one embodiment, the composition further comprises a solvent system toform an ink.

In one embodiment, the composition further comprises a solvent system toform an ink, wherein the solid content of the ink is about 0.5 to about5 wt/wt % total solids. In one embodiment, the composition furthercomprises a solvent system to form an ink, and the solvent systemcomprises toluene, o-xylene, chlorobenze, or mixtures thereof assolvent. In one embodiment, the intractable groups are polymerizablegroups, and the polymerizable groups are reacted. In one embodiment, acomposition is prepared by reaction of the first and second compounds ofthe composition as described herein. In one embodiment, the compositionfurther comprises at least one third compound, different from the firstand second compounds, which activates a polymerization reaction for thecomposition. In one embodiment, the composition further comprises atleast one third compound, different from the first and second compounds,which comprises para-styrene units. In one embodiment, the compositionfurther comprises at least one third arylamine compound, different fromthe first and second arylamine compounds, wherein the third arylaminecompound has only one crosslinking group. In one embodiment, thecomposition further comprises at least one third arylamine compound,different from the first and second arylamine compounds, wherein thethird arylamine compound has three or more crosslinking groups. In oneembodiment, the composition further comprises at least one thirdarylamine compound, wherein the third arylamine compound has a lowerLUMO and lower or similar HOMO compared to the first and secondcompounds.

Another embodiment provides a composition comprising: at least one firstcompound and at least one second compound different from the first,wherein the at least one first compound comprises a hole transportingcore which is a fluorene core or a biphenyl core, wherein the holetransporting core is covalently bonded to a first arylamine group andalso covalently bonded to a second arylamine group, and wherein the coreis further covalently bonded to at least two solubilizing groupscomprising at least four carbon atoms, and wherein the solubilizinggroups are optionally substituted with intractability groups; whereinthe at least one second compound comprises a hole transporting corewhich is a fluorene core or a biphenyl core, wherein the holetransporting core is covalently bonded to a first arylamine group andalso covalently bonded to a second arylamine group, wherein the secondcompound further comprises at least one intractability group which maybe bonded to the first arylamine group, the second arylamine group, orboth; wherein the first and second compounds have molecular weight ofabout 5,000 g/mole or less.

Another embodiment provides for a composition comprising: at least onecompound comprising a hole transporting core, wherein the core iscovalently bonded to a first arylamine group and also covalently bondedto a second arylamine group, and wherein the compound is covalentlybonded to at least one intractability group, wherein the intractabilitygroup is covalently bonded to the hole transporting core, the firstarylamine group, the second arylamine group, or a combination thereof,and wherein the compound has a molecular weight of about 5,000 g/mole orless.

In one embodiment, the compound comprises at least three intractabilitygroups, and at least one intractability group is covalently bonded tothe hole transport core, and at least one intractability group iscovalently bonded to the first arylamine group, and at least oneintractability group is covalently bonded to the second arylamine group.In one embodiment, the intractability group is covalently bonded to thehole transport core but not the first arylamine group or the secondarylamine group. In one embodiment, the intractability group iscovalently bonded to the first arylamine group, the second arylaminegroup, or both, but is not bonded to the hole transport core.

In one embodiment, the compound comprises one intractability group. Inone embodiment, the compound comprises two intractability groups. In oneembodiment, the compound comprises three or more intractability groups.In one embodiment, the compound's molecular weight is about 2,000 orless. In one embodiment, the compound's molecular weight is about 400 toabout 2,000. In one embodiment, the compound's molecular weight is about2,000 to about 5,000.

In one embodiment, the hole transporting core comprises at least twoaryl or heteroaryl rings. In one embodiment, the hole transporting corecomprises at least three aryl or heteroaryl rings. In one embodiment,the hole transport core comprises only carbocyclic rings. In oneembodiment, the hole transport core comprises at least one spiro moiety.In one embodiment, the hole transport core comprises at least onethiophene moiety. In one embodiment, the hole transport core comprisesat least two thiophene moieties. In one embodiment, the hole transportcore comprises at least one benzodithiophene moiety. In one embodiment,the hole transport core comprises at least one heteroarylmoietycomprising at least one nitrogen. In one embodiment, the hole transportcore comprises at least one heteroarylmoiety comprising at least twonitrogens. In one embodiment, the hole transport core comprises at leastone piperazine core. In one embodiment, the hole transport corecomprises at least one pyrrole ring. In one embodiment, the holetransport core comprises at least two pyrrole rings. In one embodiment,the hole transport core comprises at least one silole ring. In oneembodiment, the hole transport core comprises at least two silole rings.In one embodiment, the hole transport core comprises at least threefused rings. In one embodiment, the hole transport core comprises atleast five fused rings. In one embodiment, the hole transport core isfunctionalized with at least one solubilizing group. In one embodiment,the hole transport core is functionalized with at least two solubilizinggroups. In one embodiment, the hole transport core is functionalizedwith at least one solubilizing group which has a least four carbonatoms. In one embodiment, the hole transport core is functionalized withat least one solublizing group which as an alkylene group comprising atleast four carbon atoms. In one embodiment, the first and secondarylamine group are the same arylamine group. In one embodiment, each ofthe first and second arylamine groups are independently represented by—N(R1)(R2), wherein R1 and R2 are optionally substituted aryl orheteroaryl groups which may be the same or different.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted phenyl group. In one embodiment, each ofthe first and second arylamine groups are independently represented by—N(R1)(R2), wherein at least one of R1 and R2 is an optionallysubstituted biphenyl group. In one embodiment, each of the first andsecond arylamine groups are independently represented by —N(R1)(R2),wherein at least one of R1 and R2 is an optionally substituted carbazolegroup. In one embodiment, each of the first and second arylamine groupsare independently represented by —N(R1)(R2), wherein —N(R1)(R2) form anoptionally substituted carbazole group. In one embodiment, each of thefirst and second arylamine groups are independently represented by—N(R1)(R2), wherein at least one of R1 and R2 is an optionallysubstituted naphthyl group. In one embodiment, each of the first andsecond arylamine groups are independently represented by —N(R1)(R2),wherein at least one of R1 and R2 is an optionally substitutedthienobenzene group. In one embodiment, each of the first and secondarylamine groups are independently represented by —N(R1)(R2), wherein atleast one of R1 and R2 is an optionally substituted fluorene group. Inone embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted group comprising at least two fusedaromatic rings.

In one embodiment, the intractability group comprises a crosslinkinggroup. In one embodiment, the intractability group comprises anon-crosslinking group. In one embodiment, the intractability groupcomprises at least one ethylenically unsaturated moiety. In oneembodiment, the intractability group comprises a vinyl group. In oneembodiment, the intractability group comprises a benzocyclobutane group.In one embodiment, the intractability group comprises an indenyl group.In one embodiment, the intractability group comprises a a quaternaryammonium group. In one embodiment, the intractability group comprises aa quaternary ammonium group comprising a tetraarylborate anion. In oneembodiment, the intractability group comprises a a quaternary ammoniumgroup comprising a pentafluorophenylborate anion.

In one embodiment, the compound has a glass transition temperature ofabout 200° C. or less. In one embodiment, the compound is a firstcompound, and the composition further comprises at least one additionalsecond compound, different from the first compound, which activates apolymerization reaction for the composition.

In one embodiment, the compound is a first compound, and the compositionfurther comprises at least one additional second compound, differentfrom the first compound, which comprises para-styrene units. In oneembodiment, the compound is a first compound, and the compositionfurther comprises at least one additional second arylamine compound,different from the first arylamine compound, wherein the secondarylamine compound has only one crosslinking group. In one embodiment,the compound is a first compound, and the composition further comprisesat least one second arylamine compound, different from the firstarylamine compound, wherein the second arylamine compound has three ormore crosslinking groups. In one embodiment, the compound is a firstcompound, and the composition further comprises at least one secondarylamine compound, wherein the second arylamine compound has a lowerLUMO and lower or similar HOMO compared to the first and compound.Another embodiment provides a method comprising: providing a substratecomprising a hole injection layer, coating the substrate with at leastone ink comprising at least one hole transport material comprisingintractability groups to form a coated substrate, heating the coatedsubstrate.

In one embodiment, the ink is subjected to pre-crosslinking beforecoating the ink on the substrate. In one embodiment, the ink issubjected to thermal pre-crosslinking before coating the ink on thesubstrate. In one embodiment, the ink is subjected to thermalpre-crosslinking to form a gel before coating the ink on the substrate.In one embodiment, the ink is subjected to thermal pre-crosslinking atat least 150° C. to form a gel before coating the ink on the substrate.In one embodiment, the ink is subjected to UV light pre-crosslinkingbefore coating the ink on the substrate. In one embodiment, the coatedsubstrate is subjected to UV light to induce pre-crosslinking beforeheating the coated substrate. In one embodiment, the coated substrate isheated to at least 200° C. In one embodiment, the coated substrate isheated to at least 250° C.

In one embodiment, after heating the coated substrate shows a uniformdefect free continuous film coated on top of a substrate coated withhole injection layer in the optical microscope. In one embodiment, afterheating the coated substrate shows a uniform defect free continuous filmcoated on top of a substrate coated with a non-aqueous hole injectionlayer in the optical microscope. In one embodiment, after heating thecoated substrate is stable to toluene solvent wash so that retains atleast 90% of initial thickness after toluene is spun on the substratefor one minute and then dried for five minutes at 100° C. In oneembodiment, after heating the coated substrate is stable to toluenesolvent wash so that retains at least 95% of initial thickness aftertoluene is spun on the substrate for one minute and then dried for fiveminutes at 100° C. In one embodiment, the coating of the coatedsubstrate before crosslinking shows a Tg of 200° C. or less. In oneembodiment, the coating of the coated substrate before crosslinkingshows a Tg of 150° C. or less.

In one embodiment, the hole injection layer is an aqueous hole injectionlayer. In one embodiment, the hole injection layer is a non-aqueous holeinjection layer. In one embodiment, the hole injection layer comprises apolymer. In one embodiment, the hole injection layer comprises aconjugated polymer. In one embodiment, the hole injection layercomprises a polythiophene. In one embodiment, the hole injection layercomprises a polythiophene comprising at least one alkoxy substituent. Inone embodiment, the hole injection layer comprises a sulfonatedpolythiophene. In one embodiment, the hole injection layer comprises apolymeric arylamine. In one embodiment, the hole injection layercomprises a regioregular polythiophene. In one embodiment, the holeinjection layer comprises a conjugated polymer which is soluble inwater. In one embodiment, the hole injection layer comprises aconjugated polymer which is soluble in organic solvent.

In one embodiment, the method is further comprising the step of coatingan emitting layer on the coated substrate.

In one embodiment, the ink comprises at least two hole transportmaterials comprising intractability groups. In one embodiment, the inkcomprises at least two hole transport materials each comprising adifferent intractability group.

In one embodiment, the ink comprises a composition according to any ofthe hole transport compounds described herein. In one embodiment, theink comprises a composition comprising at least two hole transportcompounds as described herein.

In one embodiment, the compound is a first compound, and the compositionfurther comprises at least one additional second compound, differentfrom the first compound, which activates a polymerization reaction forthe composition. In one embodiment, the compound is a first compound,and the composition further comprises at least one additional secondcompound, different from the first compound, which comprisespara-styrene units. In one embodiment, the compound is a first compound,and the composition further comprises at least one additional secondarylamine compound, different from the first arylamine compound, whereinthe second arylamine compound has only one crosslinking group. In oneembodiment, the compound is a first compound, and the compositionfurther comprises at least one second arylamine compound, different fromthe first arylamine compound, wherein the second arylamine compound hasthree or more crosslinking groups. In one embodiment, the compound is afirst compound, and the composition further comprises at least onesecond arylamine compound, wherein the second arylamine compound has alower LUMO and lower or similar HOMO compared to the first and compound.

In one embodiment, the intractability groups are polymerizable groups.

An advantage for at least one embodiment is to provide high quality HTLfilms on different HIL layers including HIL layers that are relativelydifficult to coat with high quality films.

An advantage for at least one embodiment is to provide stable HTL filmson different HIL layers.

An additional advantage for at least one embodiment is to provide OLEDdevices with good lifetime and efficiency.

An additional advantage for at least one embodiment is to enable betterfilm formation for solution EML layers coated on top of the holetransport layer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates one embodiment for an image on top of Plexcore® OCHIL (aqueous) 500× Magnification.

FIG. 2 illustrates one embodiment for an initial film formation onnon-aqueous HIL (500×).

FIG. 3 illustrates one embodiment for pre-polymer by cross-linkingreaction of PLX-D (500×), with film annealing 200° C.

FIG. 4 illustrates an embodiment for UV-Modified ink (500×).

FIG. 5 illustrates an additional embodiment for a modified crosslinkingprocess (500×).

FIG. 6 illustrates an additional embodiment for PLX-C (500×), filmannealed at 200° C.

FIG. 7 illustrates an additional embodiment for PLX-B (500×), filmannealed at 200° C.

FIG. 8 illustrates relative lifetime with HTL blending ratio, forseveral embodiments.

FIG. 9 illustrates relative lifetime with HTL for several inkformulations.

FIG. 10 illustrates a schematic of synthesis strategy.

FIG. 11 illustrates an embodiment for an OLED device.

DETAILED DESCRIPTION Introduction

All references cited herein are incorporated by reference in theirentirety.

Filed on the same day herewith is U.S. patent application Ser. No.______ filed Jul. 1, 2011 entitled “HOLE TRANSPORT COMPOSITIONS ANDRELATED DEVICES AND METHODS (II)” (assignee: Plextronics), which ishereby incorporated by reference in its entirety.

Organic electronics devices, including OLEDs, as well as materials tomake organic electronic devices including hole injection layers and holetransport layers, are described in, for example, the following patentpublications assigned to Plextronics, Inc.: WO 2006/036,755; WO2006/086,480; WO 2008/073,149; WO 2009/126,918; WO 2009/111675; WO2009/111339; WO 2010/051,259; WO 2010/059,240; WO 2010/059,646; and WO2010/062,558. OLED devices can comprise a variety of sub-categoriesincluding, for example, PLEDs, SMOLEDs, PHOLEDs, WOLEDs, and the like.OLED devices, materials, and methods are also described in, for example,(1) Highly Efficient OLEDS with Phosphorescent Materials (Ed. H.Yerrin), 2008, Wiley-VCH, (2) Organic Light Emitting Devices: Synthesis,Properties, and Applications (Eds. Mullen, Scherf), 2006, (3) OrganicLight Emitting Methods and Devices, (Li and Meng), 2007, CRC.

Electroluminescent devices are described in, for example, Friend et al.,“Electroluminescence in Conjugated Polymers,” Nature, 397, 121-128, Jan.14, 1999. Hole injection and transport are described in, for example,Shen et al., “How to Make Ohmic Contact to Organic Semiconductors,”ChemPhysChem, 2004, 5, 16-25. OLED devices are described in, forexample, Forrest, “The Path to Ubiquitous and Low-Cost OrganicElectronic Appliances on Plastic,” Nature, 428, Apr. 29, 2004, 911-918.

Compounds and units within compounds which provide hole transport areknown in the art. See, for example, U.S. Pat. Nos. 5,034,296; 5,055,366;5,149,609; 5,589,320; 5,759,709; 5,895,692; and 7,125,633, as well as USPatent Publication Nos. 2005/0184287 and 2008/0286566. Hole transportmaterials, morphology, and devices (including arylamine compounds) arealso described extensively in “Charge Carrier Transporting MolecularMaterials and their Applications in Devices,” Shirota et al., Chem.Rev., 2007, 107, 953-1010.

Part I

Description of Single Hole Transporting Compounds with a Variety ofCore, Arylamine, and Intractability Groups

Individual hole transport materials or compounds are described. Inaddition, mixtures of two or more hole transport materials are alsodescribed.

Hole transport materials and compounds are known in the art. Theytypically comprise pi-electron systems. A leading example of a holetransport material is the arylamine set of compounds.

One embodiment provides, for example, a composition comprising: at leastone compound comprising a hole transporting core, wherein the core iscovalently bonded to a first arylamine group and also covalently bondedto a second arylamine group, and wherein the compound is covalentlybonded to at least one intractability group, wherein the intractabilitygroup is covalently bonded to the hole transporting core, the firstarylamine group, the second arylamine group, or a combination thereof,and wherein the compound has a molecular weight of about 5,000 g/mole orless.

The hole transporting core, arylamine, and intractability groups aredescribe more below.

Hole Transporting Core

The hole transporting core can be a bivalent, trivalent, or highervalent group which links at least to a first and a second arylaminegroup. This compound arrangement can be also represented by A1-C-A2,wherein A1 represents a first arylamine group, and A2 represents asecond arylamine group, and C represents the hole transporting core. Theone or more intractability groups can be bonded to one or more of A1, C,and/or A2. In addition, the compound can comprise additional arylaminegroups either in the hole transporting core or in the groups linked tothe arylamine groups outside of the core.

A variety of aryl or heteroaryl groups can be used in the holetransporting core. Examples of aryl and heteroaryl groups, which can beoptionally substituted, are known in the art and include benzene,naphthalene, anthracene, phenanthrene, perylene, tetracene, pyrene,benzpyrene, chrysene, triphenylene, acenaphtene, fluorene, and thosederived therefrom. Examples of heteroaryls include furan, benzofuran,thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole,oxadiazole, oxazole, thiazole, tetrazole, indole, cabazole,pyrroloimidazole, pyrrolopyrazole, pyrrolopyrole, thienopyrrole,thienothiophene, furopyrrole, furofuran, thienofuran, benzoisoxazole,benzoisothiazole, benzoimidazole, pyridine, pyrazine, pyridazine,pyrimidine, triazine, quinoline, isoquinoline, cinnnoline, quinoxaline,phenanthridine, benzoimidazole, perimidine, quinazoline, quinazolinone,azulene, and those derived therefrom. The aryl or heteroaryl groups cancomprise fused ring systems.

Aryl and heteroaryl groups can be optionally substituted with a varietyof substituents and/or solubilizing groups. Examples can be(independently) H, F, alkyl, aryl, alkoxy, aryloxy, fluoroalkyl,fluoroaryl, fluoroalkoxy, fluoroaryloxy, as well as intractabilitygroups described herein. Substituents on neighboring rings can fusetogether to form a ring.

In one embodiment, for example, the hole transporting core comprises atleast two aryl or heteroaryl rings. In one embodiment, the holetransporting core comprises at least three aryl or heteroaryl rings. Inone embodiment, the hole transport core comprises only carbocyclicrings. In one embodiment, the hole transport core comprises at least onespiro moiety. Spiro moieties in a hole transport compounds are describedin, for example, US Pat. Pub. No. 2004/0106004 (Li).

The hole transporting core can comprise all carbon and hydrogen atoms.Alternatively, the hole transporting core can comprise heteroatoms suchas O, S, N, P, Si, Se, Te, and the like. In one embodiment, the holetransport core comprises at least one thiophene moiety. In oneembodiment, the hole transport core comprises at least two thiophenemoieties. In one embodiment, the hole transport core comprises at leastone benzodithiophene moiety. In one embodiment, the hole transportingcore comprises both O and S heteroatoms, as described furtherhereinbelow.

In one embodiment, the hole transport core comprises at least oneheteroarylmoiety comprising at least one nitrogen. In one embodiment,the hole transport core comprises at least one heteroarylmoietycomprising at least two nitrogens. In one embodiment, the hole transportcore comprises at least one piperazine moiety. In one embodiment, thehole transport core comprises at least one pyrrole ring. In oneembodiment, the hole transport core comprises at least two pyrrolerings.

In one embodiment, the hole transport core comprises at least one silolering. In one embodiment, the hole transport core comprises at least twosilole rings.

The hole transporting core can comprise fused rings. In one embodiment,the hole transport core comprises at least two, or at least three, or atleast four fused rings. In one embodiment, the hole transport corecomprises at least five fused rings.

One or more substituent groups can be covalently bonded to the holetransporting core to increase solubility. A common example of such asolubilizing group is an optionally substituted alkyl or heteroalkylmoiety (an alkyl group, if used in a bivalent situation as spacer, canbe also called alkylene; for example, propyl can be a propylene spacer).For example, C4 to C30, or C4 to C20, or C4 to C12 solublizing groupscan be used. Heteroatoms include, for example, oxygen, nitrogen, andsulfur. One skilled in the art can examine the impact of the substituentgroup on solubility. In one embodiment, the hole transport core isfunctionalized with at least one solubilizing group. In one embodiment,the hole transport core is functionalized with at least two solubilizinggroups. In one embodiment, the hole transport core is functionalizedwith at least one solubilizing group which has a least four carbonatoms. In one embodiment, the hole transport core is functionalized withat least one solublizing group which as an alkylene group comprising atleast four carbon atoms. Other solubilizing groups are shown in thestructures herein.

A variety of hole transporting cores are shown throughout the presentdisclosure including compounds based on combinations of substructuresshown in Table 1 (below) and the working examples. Particular examplesof hole transporting core groups comprising sulfur (along withrepresentative arylamine groups, but without intractability groupsexcept for as shown) are shown below, and show the hole transportingcore covalently bonded to two arylamine groups:

Compound/Core A-1 (no intractability groups shown)

Compound/Core B-1 (no intractability groups shown). The branched alkylsolubilizing groups on the core can be varied including for exampleC4-C20 optionally substituted groups including alkyl groups.

Compound/Core C-1 (no intractability groups shown). The branched alkylsolubilizing groups on the core can be varied including for exampleC4-C20 optionally substituted groups including alkyl groups.

Compound/Core D-1 (no intractability groups shown).

Compound/Core E-1, wherein two intractability groups are shown.

First and Second Arylamine Groups

Arylamine groups are generally known in the art. See, for example, USPat. Pub. No. 2011/0017988 Yasukawa et. A1 and other references citedherein. The arylamine group will have one valency on the nitrogen bondedto the hole transport core. The other two valencies on the nitrogen arebonded to aryl groups. This can be represented by N(R1)(R2)(R3), whereinR1-R3 are aryl groups which can be the same or different, independentlyof each other. The arylgroup can be a group free of heteroatoms or canbe a heteroaryl group comprising at least one heteroatom. A variety ofarylamine groups are shown throughout this disclosure including Table 1.

In one embodiment, the first and second arylamine groups are the samearylamine group. In one embodiment, the first and second arylaminegroups are different arylamine groups.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein R1 and R2 areoptionally substituted aryl or heteroaryl groups which may be the sameor different.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted phenyl group (the remaining valency onthe arylamine is linked to the hole transporting core).

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted biphenyl group.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted carbazole group.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein —N(R1)(R2) form anoptionally substituted carbazole group.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted naphthyl group.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted thienobenzene group.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted fluorene group.

In one embodiment, each of the first and second arylamine groups areindependently represented by —N(R1)(R2), wherein at least one of R1 andR2 is an optionally substituted group comprising at least two fusedaromatic rings.

Intractability, Polymerizable, and Crosslinking Groups

Intractability of hole transport materials is known in the art. See, forexample, US Pat. Pub. Nos. 2009/0256117; 2010/0273007; and 2010/0292399.Intractability groups allow the materials to be sufficiently chemicaland solvent resistant, allowing for solution processing.

In one embodiment, the intractability group comprises a polymerizable orcrosslinking group. The crosslinking group allows for a covalent linkagebetween molecules and buildup of molecular weight to provideintractable, chemically resistant, and solvent resistant materials. Inone embodiment, the intractability group comprises a non-crosslinkinggroup. A non-crosslinking group can be a salt group, comprising cationand anion. Organic anions can be used including borates. Ammoniumcations can be used.

In one embodiment, the intractability group can be linked to the rest ofthe molecule via a spacer. Examples of spacers include solubilizinggroups, described herein, including alkylene groups. In one embodiment,the intractability group is a vinyl group, but is either linked to anon-aromatic group or is only linked to a single aromatic group as in astyrene conformation. In one embodiment, the intractability group isseparated from a larger delocalized structure such as fused aromaticring systems. This may, in some cases, improve stability. In oneembodiment, the styrene group can be linked to the hole transportingcore via a non-conjugated spacer such as an alkylene moiety.

In one embodiment, the intractability group comprises at least oneethylenically unsaturated moiety. In one embodiment, the intractabilitygroup comprises a vinyl group. In one embodiment, the vinyl group islinked to an oxygen atom (vinyleneoxy group) or in another embodiment toa carbon atom which is part of an aliphatic or aromatic group (e.g.,propenyl; other examples include acryloyl, or methacryloyl). In oneembodiment, the intractability group comprises a benzocyclobutane group.In one embodiment, the intractability group comprises an indene group(or indenyl, e.g., intractability group 4 in Table 1).

In one embodiment for a non-crosslinking group, the intractability groupcomprises a a quaternary ammonium group. In one embodiment, theintractability group comprises a a quaternary ammonium group comprisinga tetraarylborate anion. In one embodiment, the intractability groupcomprises a a quaternary ammonium group comprising apentafluorophenylborate anion. A spacer groupd can be used to providelinkage between the quaternary ammonium group and the arylamine group.Several particular embodiments for compounds with intractability groups,which are not polymerizable groups, include compounds PLX-IG1 andPLX-IG2:

Arrangement of the Intractability Groups

At least three arrangement exist for arranging the intractability groupsin the molecule with respect to the core and the arylamine groups, andrepresentative embodiments for each are described herein.

In one first embodiment, for example, the compound comprises at leastthree intractability groups, and at least one intractability group iscovalently bonded to the hole transport core, and at least oneintractability group is covalently bonded to the first arylamine group,and at least one intractability group is covalently bonded to the secondarylamine group.

In one second embodiment, for example, the intractability group is, orthe intractability groups are, covalently bonded to the hole transportcore but not the first arylamine group or the second arylamine group.

In one third embodiment, for example, the intractability group is, orthe intractability groups are, covalently bonded to the first arylaminegroup, the second arylamine group, or both, but is not bonded to thehole transport core.

Number of Intractability Groups

In one embodiment, the compound comprises one intractability group. Inone embodiment, the compound comprises two or more intractabilitygroups. In other embodiments, the compound comprises three, four, five,or six or more intractability groups.

No particular upper limit exists, but the number of intractabilitygroups can be 12 or less, or 10 or less, or 8 or less, or 6 or less.

Molelcular Weight

In addition, the molecular weight (g/mol) for the hole transportcompound can be adapted for an application. The molecular weight can be,for example, about 5,000 g/mol or less, or about 4,000 g/mol or less, orabout 3,000 g/mol or less, or about 2,000 g/mol or less, or about 1,000g/mol or less. In one embodiment, the compound's molecular weight isabout 400 g/mol to about 5,000 g/mol, or about 400 g/mol to about 2,000g/mol. In one embodiment, the compound's molecular weight is about 2,000g/mol to about 5,000 g/mol. The molecular weight can be greater than,for example, about 250 g/mol, or greater than about 400 g/mol.

Table with Examples of HTL Core, Arylamine, and Intractability Groups

The following Table 1 provides specific examples of hole transportingcore groups, the arylamine groups (whether first or second arylaminegroups), and intractability groups. These can be arranged in anycombination which is synthetically viable. For the HTL core groups shownin Table 1, the dangling bonds represent bonding sites for the arylaminegroup at the nitrogen atom. The R or R′ groups shown in Table 1 can be,independently of each other, substituent or solubilizing groups asdescribed herein including, for example, C1-C20 groups, or C4-C20groups. The R or R′ groups can be saturated or unsaturated, linear,cyclic, branched, and optionally substituted with functional groupsknown in the art.

TABLE 1 Arylamine Intractability HTL Core Group Groups Groups (IG) 1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

Additional Specific Compounds

Additional specific hole transporting compounds are shown below (notethat the C₆H₁₃ groups are shown below as representative; they could be,for example, any R groups such as C4 to C20 alkyl groups includinglinear or branched or cyclic):

Part II Mixture of Hole Transporting Compounds

In Part II, compositions can be prepared which comprise two or more holetransporting compounds. Compounds as described above in Part I can beselected for use in mixtures including binary mixtures. In particular,however, for compounds in these mixtures, for example, the core cancomprise, for example, fluorene, phenyl, or biphenyl moieties. Inparticular, the fluorene core is of interest for the mixtures. Thecareful formulation of the mixtures can provide for good coating of HILlayers including non-aqueous HIL layers.

For example, one embodiment provides a composition comprising: at leastone first compound and at least one second compound different from thefirst, wherein the at least one first compound comprises a holetransporting core which is a fluorene core, wherein the holetransporting core is covalently bonded to a first arylamine group andalso covalently bonded to a second arylamine group, and wherein the coreis further covalently bonded to at least two solubilizing groupscomprising at least four carbon atoms, and wherein the solubilizinggroups are optionally substituted with intractability groups; whereinthe at least one second compound comprises a hole transporting corewhich is a fluorene core, wherein the hole transporting core iscovalently bonded to a first arylamine group and also covalently bondedto a second arylamine group, wherein the second compound furthercomprises at least one intractability group which may be bonded to thefirst arylamine group, the second arylamine group, or both; and whereinthe first and second compounds have molecular weight of about 5,000g/mole or less.

Relative Mass Proportion of First and Second Compounds

The relative mass proportion of the first and second compounds can beadapted for a particular application. For example, in one embodiment,the relative amounts of the first and second compounds are about 99:1 toabout 1:99 by weight, respectively. In another embodiment, the relativeamounts of the first and second compounds are about 90:10 to about 10:90by weight, respectively. In another embodiment, the relative amounts ofthe first and second compounds are about 80:20 to about 20:80 by weight,respectively. In another embodiment, the relative amounts of the firstand second compounds are about 70:30 to about 30:70 by weight,respectively. In another embodiment, the relative amounts of the firstand second compounds are about 60:40 to about 40:60 by weight,respectively.

In one embodiment, the relative amounts of the first and secondcompounds are about 20:80 to about 40:60 by weight, respectively.

In one embodiment, the relative amounts of the first and secondcompounds are about 99:1 to about 80:20 by weight, respectively.

In one embodiment, the relative amounts of the first and secondcompounds are about 40:60 to about 60:40 by weight, respectively.

In one embodiment, the relative amounts of the first and secondcompounds are about 80:20 to about 60:40 by weight, respectively.

Symmetry of First and Second Arylamine Groups

In one embodiment, for the first compound, the first and send arylaminegroups are the same group. In one embodiment, for the second compound,the first and send arylamine groups are the same group. In oneembodiment, the first and second arylamine groups are different for thefirst and second compounds.

Molecular Weights

The molecular weight (g/mol) of the hole transporting compound used inmixtures can be adapted for a particular application and can beindependently selected for each compound. For example, in oneembodiment, the molecular weight of the first compound is about 5,000 orless, and the molecular weight of the second compound is about 5,000 orless. In another embodiment, the molecular weight of the first compoundis about 3,000 or less, and the molecular weight of the second compoundis about 3,000 or less. In one embodiment, the molecular weight of thefirst compound is about 2,000 or less, and the molecular weight of thesecond compound is about 2,000 or less. In one embodiment, the molecularweight of the first compound is about 1,000 or less, and the molecularweight of the second compound is about 1,000 or less. The molecularweight of the first and second compounds can be, for example, at leastabout 100, or at least about 200, or at least about 300, or at leastabout 400, or at least about 500.

Number of Arylamine Groups

In the mixtures, the hole transporting compounds can comprise first andsecond arylamine groups. In one embodiment, the first compound has onlytwo arylamine groups, and the second compound has only two arylaminegroups. In another embodiment, the first or second compound has three,four, five, or even six or more aryl amine groups. The core, which linksthe first and second arylamine groups, can comprise third, forth, fifth,and sixth or more arylamine groups.

Bonding Sites on the Core Fluorene

The hole transporting core can be based on a fluorene moiety, and thenumbering scheme for fluorene substituents is known in the art. In oneembodiment, the core fluorene groups of the first and second compoundsare bonded to the arylamines at the 2 and 7 positions of the fluorenegroup, and the core fluorene group is bonded to the substituents orsolubilizing groups at the 9 position.

In one embodiment, the two substituents or solubilizing groups bonded tothe fluorene core are the same groups. In one embodiment, the twosubstituents or solubilizing groups bonded to the fluorene core aredifferent groups. The two or more substituents or solubilizing groupscan be selected independently of each other. They can be, for example,C4 to C20 groups.

Length of Substituents or Solubilizing Groups—First Compound

The length of the substituents or solubilizing groups can be adapted fora particular application. For example, for the first compound, the twosubstituents or solubilizing groups can comprise at least four carbonatoms, at least five carbon atoms, or at least six carbon atoms, or atleast seven carbon atoms, or at least eight carbon atoms. Thesubstitutent or solubilizing group can be, for example, a C4-C20 groupincluding a straight chain, a branched group, or a cylic group. Examplesinclude optionally substituted alkyl groups. Unsaturated groups can bepresent including double or triple bonds.

Distribution of the Intractability Groups on Arylamines—Second Compound

In one embodiment, the second compound comprises at least oneintractability group which is bonded to the first arylamine group, andat least one intractability group which is bonded to the secondarylamine group.

Types of Intractability Groups

In one embodiment, the intractable groups are crosslinking polymerizablegroups. In another embodiment, the intractable groups are ethylenicallyunsaturated groups. They can be vinyl including vinyl bonded to phenylcreating a styrene unit, whether para or meta substituted.

Types of Intractability Groups—Second Compound

In one embodiment, the intractability group for the second compound isvinyl. In one embodiment, the intractability group for the secondcompound is vinyl which is covalently bonded to a phenyl ring to form astyrene unit.

Types of Groups Bonded to the Arylamine

In one embodiment, at least one of the arylamine groups comprises anoptionally substituted naphthyl group bonded to nitrogen. In at leastone embodiment, at least one of the arylamine groups comprises an bothan optionally substituted naphthyl group and an optionally substitutedphenyl group bonded to nitrogen.

Solubility of First and Second Compounds

In one embodiment, the solubility of the first compound can be at least0.1 mg/mL, or at least 0.9 mg/mL, or at least or at least 2 mg/mL, asmeasured by dissolving the hole transport material in toluene or othersuitable solvent at 25° C.

In one embodiment, the solubility of the first compound can be at least0.1 mg/mL, or at least 0.9 mg/mL, or at least 2 mg/mL, as measured bydissolving the hole transport material in toluene or other suitablesolvent at 25° C.

Embodiments Including PLX-A (Working Examples)

In one embodiment, for the first compound, the solubilizing group issubstituted with the intractability group, and for the second compoundthe core further comprises at least two solubilizing groups comprisingat least four carbon atoms.

In one embodiment, the relative amounts of the first and secondcompounds are about 20:80 to about 40:60 by weight, respectively.

In one embodiment, the relative amounts of the first and secondcompounds are about 25:75 to about 35:65 by weight, respectively.

In one embodiment, the first compound the intractability group isbenzocyclobutane.

In one embodiment, for the second compound the core further comprises atleast two solubilizing groups comprising at least eight carbon atoms.

In one embodiment, for the second compound, the solubilizing groups donot comprise intractability groups.

In one embodiment, the first compound and the second compound comprisedifferent intractability groups.

In one embodiment, the first compound is represented by:

In one embodiment, the first compound is represented by:

In one embodiment, the second compound is represented by:

In one embodiment, the first compound is represented by:

and the second compound is represented by:

Embodiments Including INK B (Working Examples)

In one embodiment, for the first compound, the solubilizing group of thecore is unsubstituted with intractability group.

In one embodiment, the relative amounts of the first and secondcompounds are about 99:1 to about 80:20 by weight, respectively. In oneembodiment, the relative amounts of the first and second compounds areabout 95:5 to about 85:15 by weight, respectively.

In one embodiment, for the first compound the intractability group is onat least one of the arylamine groups and is vinyl.

In one embodiment, for the second compound the core further comprises togroups bonded to fluorene which are C3, C2, or C1 groups.

In one embodiment, for the second compound intractability groups bondedto the first and second arylamine which are vinyl bonded to phenyl toform a para-styrene.

In one embodiment, the first compound does not comprise intractabilitygroups bonded to the core.

In one embodiment, the first compound is represented by:

In one embodiment, the second compound is represented by:

In one embodiment, the first compound is represented by:

and the second compound is represented by:

Embodiments Including INK C (Working Examples)

In one embodiment, for the first compound, the solubilizing group issubstituted with the intractability group and for the second compound,the core does not comprise at least two solubilizing groups comprisingat least four carbon atoms.

In one embodiment, the relative amounts of the first and secondcompounds are about 80:20 to about 20:80 by weight, respectively. In oneembodiment, the relative amounts of the first and second compounds areabout 60:40 to about 40:60 by weight, respectively.

In one embodiment, for the first compound the intractability group isvinyl. In one embodiment, for the first compound the intractabilitygroup is vinyl bonded to a phenyl to form a styrene unit.

In one embodiment, for the second compound the core further comprises togroups bonded to fluorene which are C3, C2, or C l groups.

In one embodiment, for the second compound intractability groups bondedto the first and second arylamine which are vinyl bonded to phenyl toform a para-styrene.

In one embodiment, the first compound is represented by:

In one embodiment, the second compound is represented by:

In one embodiment, the first compound is represented by:

and the second compound is represented by:

Polymerization Activators

The hole transporting formulations based on compounds of Parts I and IIcan be adapted with use of additional components such as polymerizationactivators.

In one embodiment, the compound of Part I is a first compound, and thecomposition further comprises at least one additional second compound,different from the first compound, which activates a polymerizationreaction for the composition.

In one embodiment, the compound of Part I is a first compound, and thecomposition further comprises at least one additional second compound,different from the first compound, which comprises para-styrene units.

In one embodiment, the compound of Part I is a first compound, and thecomposition further comprises at least one additional second arylaminecompound, different from the first arylamine compound, wherein thesecond arylamine compound has only one crosslinking group.

In one embodiment, the compound of Part I is a first compound, and thecomposition further comprises at least one second arylamine compound,different from the first arylamine compound, wherein the secondarylamine compound has three or more crosslinking groups.

In one embodiment, the compound of Part I is a first compound, and thecomposition further comprises at least one second arylamine compound,wherein the second arylamine compound has a lower LUMO and lower orsimilar HOMO compared to the first and compound.

For example, in one embodiment for a binary blend, the compositionfurther comprises at least one third compound, different from the firstand second compounds, which activates a polymerization reaction for thecomposition.

In one embodiment for a binary blend, for example, the compositionfurther comprises at least one third compound, different from the firstand second compounds, which comprises para-styrene units.

Examples of activators or compounds having the vinyl group in a paraposition on the styrene moiety are shown below:

The activator can be used in amounts of, for example, 20 wt. % or less,or 10 wt. % or less, or 5 wt. % or less, with respect to the holetransporting compounds.

One Crosslinking Group

In another formulation strategy, the degree of crosslinking forformulations based on the compounds of Parts I and II can be adapted tohelp control parameters such as film shrinkage. For example, in oneembodiment, the composition further comprises at least one thirdarylamine compound, different from the first and second arylaminecompounds, wherein the third arylamine compound has only onecrosslinking group. The crosslinking moiety can be a vinyl group in apara position for a styrene.

Examples include:

(again, the hexyl groups are representatitve; they can be, for example,any R C4 to C20 group).

Three or More Crosslinking Groups

In still another formulation strategy, the degree of crosslinking informulations based on the compounds in Parts I and II can be adaptedalso to control the solvent resistance including increasing solventresistance. For example, in one embodiment, the composition furthercomprises at least one third arylamine compound, different from thefirst and second arylamine compounds, wherein the third arylaminecompound has three or more crosslinking groups, or four or morecrosslinking groups, or five or more crosslinking groups. Thecrosslinking groups can be, for example, vinyl groups of a styrene unit.Examples include:

One can adapt the degree of crosslinking per molecular unit to provide adesired result.

Stabilizer

In one embodiment, the composition further comprises at least one thirdarylamine compound, wherein the third arylamine compound has a lowerLUMO and lower or similar HOMO compared to the first and secondcompounds. Inclusion of such a moiety can help in quenching anyelectrons leaked into the hole transport layer from the emissive layer,hence stabilizing the HTL from any degradation because of electroncurrent.

An example of a stabilizer is:

Exclusion of Polymer

The composition can be free or substantially free of polymeric materialsbefore crosslinking For example, the composition can be free orsubstantially free of materials having a molecular weight of more than5,000 g/mole or more, or free of materials having a molecular weight ofmore than 10,000 g/mol. The composition, before crosslinking, cancomprise only materials having lower molecular weights such as below5,000 g/mol, or below 2,000 g/mole, or below 1,000 g/mol. The amount ofpolymer can be less than 1 wt. %, or less than 0.1 wt. %, or less than0.01 wt. %, for example.

Purity of Materials

The compounds and materials described herein generally should bepurified as much as possible to have a good device performance. Forexample, impurities such as metals (e.g., Pd, Sn) or halogens (e.g., Cl,Br) should be reduced to less than 100 ppm, or less than 80 ppm, or lessthan 60 ppm, or less than 40 ppm, or less than 20 ppm.

Synthesis of Hole Transporting Compounds

One skilled in the art can use organic chemistry to link together thecore moiety, the arylamine moieties, and the intractability group orgroups. Synthesis is described in, for example, March's Advanced OrganicChemistry, 6^(th) Ed., Wiley, 2007, as well as in references citedherein. For example, a schematic for synthesis of hole transportingcompounds is shown in FIG. 10. Examples of major reactions for HTLsynthesis include amination, dehalogenation, deprotection, and Wittigreactions. Additional synthetic methods are shown in the workingexamples.

The hole transport formulations, mixtures, and compounds describedherein can be further processed into inks, films, and devices.

Part III Inks, Methods of Making Films and Devices Inks and SolventSystem

The compositions described herein can be used in solid or can beformulated into liquid form as inks Hence, in one embodiment, thecomposition further comprises a solvent system to form an ink. Solventsystems are known. See, for example, WO 2010/093592 (Cheon et al.).

The solid content of the ink can be adapted for a particularapplication. In one embodiment, the composition further comprises asolvent system to form an ink, wherein the solid content of the ink isat least 0.1 w/w % of solvent, or at least 0.3 w/w % of the solvent, orat least 1 w/w % of solvent.

The solvent system can comprise one solvent, two solvents, or three ormore solvents (e.g., solvent blends can be used). Organic solvents canbe used. In one embodiment, the solvent system comprises toluene assolvent.

Solvents can include aromatic hydrocarbons in the neutral and oxidizedforms. Solvents such as tetrahydrofuran, chloroform, or aromatichydrocarbons in the neutral and oxidized forms can be used. Additionalsolvents include tetrahydrofuran, chloroform, alkylated benzenes,halogenated benzenes, NMP, DMF, DMAc, DMSO, methyl ethyl ketone,cyclohexanone, chloroform, dichloromethane, acetone, THF, dioxanes,ethyl acetate, ethyl benzoate, ethylene carbonate, propylene carbonate,or combinations thereof.

For environmental compliance, one or more nonhalogenated solvents may beselected. Halogenated solvents can be substantially or totally excluded(e.g., used in less than 10%, or less than 5%, or less than 1%, or lessthan 0.1% by volume of total solvent carrier). In weighing suchadditional factors, it may be helpful to consult references such as, forexample, Cheremisnoff, N. P., Industrial Solvents Handbook, 2^(nd) Ed.(Marcel Dekker, New York, 2003); Ash, M, Handbook of Solvents, 2^(nd)Ed. (Syapse Information Resources, 2003); Wypych, G., Handbook ofSolvents (Chemical) (Noyes Publications, 2000); Hansen, C. M., Durkee,J. and Kontogeorgis, G, Hanson Solubility Parameters: A User's Handbook(Taylor and Francis, 2007); all of which are incorporated by referencein their entireties.

Solvents to be considered may include ethers (optionally substitutedwith C1-C10 alkyl chains) such as anisole, ethoxybenzene, dimethoxybenzenes and glycol ethers, such as: ethylene glycol diethers such as1,2-dimethoxy ethane, 1,2-diethoxy ethane, 1,2-dibutoxy ethane;diethylene glycol diethers such as diethylene glycol dimethyl ether,diethylene glycol diethyl ether; propylene glycol diethers such aspropylene glycol dimethyl ether, propylene glycol diethyl ether,propylene glycol dibutyl ether; dipropylene glycol diethers such asdipropylene glycol dimethyl ether, dipropylene glycol diethyl ether,dipropylene glycol dibutyl ether; also, higher analogs (tri- and tetra-)of the ethylene glycol and propylene glycol ethers mentioned above.

Still other solvents can be considered, such as ethylene glycolmonoether acetates and propylene glycol monoether acetates, wherein theether can be selected, for example, from: methyl, ethyl , n-propyl,iso-propyl, n-butyl, sec-butyl, tert-butyl, cyclohexyl. Also, higherglycol ether analogs of above list such as di-, tri- and tetra-.Examples include, but are not limited to, propylene glycol methyl etheracetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate.

Yet other possible solvents include aliphatic and aromatic ketones suchas acetonyl acetone, methyl isobutyl ketone, methyl isobutenyl ketone,2-hexanone, 2-pentanone, acetophenone, ethyl phenyl ketone,cyclohexanone, cyclopentanone.

Additional possible solvents include N,N-dimethyl formamide,N,N-dimethyl acetamide, N-methyl pyrrolidone, dimethyl sulfoxide,tetramethylene sulfoxide, acetonitrile, benzonitrile, ethylenecarbonate, propylene carbonate, and the like.

Other examples include cyclic ethers such as, for example,tetrahydropyran (THP). Solvent can be used such that polymerization ofthe solvent can be avoided. Another example is methoxyproprionitrile.

The one or more solvents can be used in varying proportions to improvethe ink characteristics such as substrate wettability, ease of solventremoval, viscosity, surface tension, and jettability.

Alternatively, it may be useful to select more than one solvent, forexample, a first solvent and a second solvent. In one example, thesolutes can have a higher solubility in the first solvent than in thesecond solvent. The hole transporting compound can also have a highersolubility in the second solvent than in the first solvent. The solventcan be selected such that the first solvent can be removed at a fasterrate than the second solvent in a drying step.

Reacted and Dried Form of Compositions

Also described herein are compositions, wherein the reactivecompositions are either partially reacted or fully reacted. For example,in one embodiment, the intractable groups are polymerizable groups, andthe polymerizable groups are reacted. In one embodiment, a compositionis prepared by reaction of the intractability groups of the first andsecond compound of the compositions described herein.

The compositions can be converted into films by methods known in theart. Hence, in one embodiment, the intractable groups are polymerizablegroups, and the polymerizable groups are reacted, and the composition isin the form of a thin film.

Methods of Forming Films

Coated substrates can be formed. One or more layers of film can be addedto a preexisting film or substrate. For example, another embodimentprovides a method comprising: providing a substrate comprising a holeinjection layer, coating the substrate with at least one ink comprisingat least one hole transport material comprising intractability groups toform a coated substrate, heating the coated substrate. The holetransport material can comprise one or more of the compositionsdescribed herein.

In one embodiment, the ink is subjected to pre-crosslinking beforecoating the ink on the substrate. In one embodiment, the ink issubjected to thermal pre-crosslinking before coating the ink on thesubstrate. In one embodiment, the ink is subjected to thermalpre-crosslinking to form a gel before coating the ink on the substrate.In one embodiment, the ink is subjected to thermal pre-crosslinking atat least 150° C. to form a gel before coating the ink on the substrate.In one embodiment, the ink is subjected to UV light pre-crosslinkingbefore coating the ink on the substrate.

In one embodiment, the coated substrate is subjected to UV light toinduce pre-crosslinking before heating the coated substrate.

In one embodiment, the coated substrate is heated to at least 200° C. Inone embodiment, the coated substrate is heated to at least 250° C.

The quality of the film can be examined by optical microscopy, lookingfor film defects, formation of aggregates and beads, dewetting of thefilm, and pinholes.

In one embodiment, which is comparative, after heating, the coatedsubstrate shows films with beads formed on the top layer interspersedwith the area of the lower film where the top hole transport layer filmhas dewetted (in the optical microscope).

In one embodiment, after heating, the coated substrate shows defectfree, smooth and continuous films conforming and wetting well on thelower lying hole injection layer (in the optical microscope).

Films can be evaluated at both low and high magnifications to isolatethe presence of both large and small scale defects and ensure an overallsmooth continuous coating.

The film formation can be carried out by methods known in the artincluding drop coating, spin coating, ink jet printing, slot diecoating, nozzle printing, screen printing, and the like.

Characterizing Films

In one embodiment, after heating the coated substrate is stable totoluene solvent wash so that retains at least 90% of the initialthickness before the wash. In one embodiment, after heating the coatedsubstrate is stable to toluene solvent wash so that retains at least 95%of the initial thickness before the wash.

In one embodiment, after heating the coated substrate is stable toimmersion in toluene for 5-10 minutes so that it retains at least 90% ofthe initial thickness before wash and does not show an increase in thethickness beyond 110% of the initial thickness.

In one embodiment, after heating the coated substrate is stable toimmersion in toluene for 5-10 minutes so that it retains at least 95% ofthe initial thickness before wash and does not show an increase in thethickness beyond 105% of the initial thickness.

The film quality (smoothness) can be evaluated by atomic forcemicroscopy, and films can show an rms roughness of 5 nm or below. TheAFM micrographs can help to ensure good film quality at the nanoscaleand also helps in understanding film morphology and its effect on deviceperformance.

On the films deposited on the substrates, other measurements can beperformed such as AC2 can be used to measure the HOMO energy of films.Absorption measurements (UV-VIS) can be done to calculate the bandgap ofthe hole transport material. The LUMO can be estimated by subtractingthe band gap from the HOMO. Also photoluminescence measurements can bedone on the hole transport films to study their emissioncharacteristics.

In one embodiment, the coating of the coated substrate shows a Tg ofless than 200° C., or less than 150° C.

Substrate and Hole Injection Layer

Solution processing for OLED fabrication is known in the art. Orthogonalsolubility principles can be used. In particular, the hole transportcompounds and formulations can be applied on top of a hole injectionlayer (HIL) material or film. The hole injection layers can be materialssoluble in water or organic solvents. Solution process can providedepositing materials from a liquid medium, including solutions,dispersions, emulsions, or other forms.

In one embodiment, the hole injection layer is an aqueous hole injectionlayer. For example, the HIL layer material can be soluble in water.

In one embodiment, the hole injection layer is a non-aqueous holeinjection layer. For example, the HIL layer material can be soluble inorganic solvent.

In one embodiment, the hole injection layer comprises a polymer. In oneembodiment, the hole injection layer comprises a conjugated polymer. Inone embodiment, the hole injection layer comprises a polythiophene. Inone embodiment, the hole injection layer comprises a polythiophenecomprising at least one alkoxy substituent. In one embodiment, the holeinjection layer comprises a sulfonated polythiophene. In one embodiment,the hole injection layer comprises a polymeric arylamine. In oneembodiment, the hole injection layer comprises a regioregularpolythiophene. In one embodiment, the hole injection layer comprises aconjugated polymer which is soluble in water. In one embodiment, thehole injection layer comprises a conjugated polymer which is soluble inorganic solvent.

For example, hole injection layers are described in the following USPatent Publications (assignee: Plextronics): 2006/0078761; 2008/0248313;2009/0256117; 2009/0230361; 2010/0108954; 20100292399; 2010/0072462;2010/0109000; 2011/0147725, which are all hereby incorporated byreference in their entireties.

Examples of aqueous hole injection layers are described in 2008/0248313(Seshadri et al.)

Examples of non-aqueous hole injection layers are described in2006/0078761 and 2009/0256117 (Seshadri et al.). For example, the HILcan be based on a 3,4-disubstituted polythiophene including apoly(3,4-dialkoxythiophene).s

OLED devices are also fabricated with emitting layers and other layersknown in the art of OLED devices. In one embodiment, the method furthercomprises the step of coating an emitting layer on the coated substrate.

In one embodiment, the ink comprises at least two hole transportmaterials comprising intractability groups. In one embodiment, the inkcomprises at least two hole transport materials each comprising adifferent intractability group. The two different intractability groupscan be adapted to function together during film formation. For example,one might react at a lower temperature, and one might react at a highertemperature. In general, one tries to have all or as many as possible ofthe intractability groups to react.

Device Fabrication and Characterization

Devices can be fabricated by methods known in the art and can becharacterized by methods known in the art.

As illustrated in FIG. 11, an organic light emitting diode can comprisea series of layers including, for example,

-   ITO: Transparent anode, typically-   HIL: Hole injection layer to facilitate charge injection-   HTL: Hole transport layer which carries charges-   EML: Emissive layer where light is emitted-   HBL: Hole blocking layer to prevent charge leakage-   ETL: Electron transport layer to facilitate charge injection-   Cathode

Layers can be supported by substrates including flexible, or rigid, ororganic, or inorganic substrates.

Additional examples of layers and devices, and related methods ofmaking, testing, and using, can be found in, for example, US PatentPublication Nos. 2005/0184287; 2006/0032528; 2008/0286566; 2009/0159877;2010/0187500; 2010/0187510; 2010/0207109; 2010/0213446; 2010/0244665; WO07076146; WO 07079103; WO 07120143; WO 07145979; WO 08024378; WO08024379; WO 08024380; WO 08106210; WO 08150872; WO 08150943; WO09018009; WO 09052085; WO 09055532; WO 09067419; WO 09097377; WO09140570.

Applications

OLEDs can be used in, for example, display or lighting applications.Other applications are described in, for example, (1) Highly EfficientOLEDS with Phosphorescent Materials (Ed. H. Yerrin), 2008, Wiley-VCH,(2) Organic Light Emitting Devices: Synthesis, Properties, andApplications (Eds. Mullen, Scherf), 2006, (3) Organic Light EmittingMethods and Devices, (Li and Meng), 2007, CRC. See also Shirota et al.,Chem. Rev., 2007, 107, 953-1010 for OLEDs, OPVs, OFETs, and otherapplications.

Embodiments from US Provisional 61/361,147

Embodiments described more fully in priority US provisional application61/361,147 filed Jul. 2, 2010 (assignee: Plextronics) are also providedfor herein including hole transport materials, and this priorityprovisional is fully incorporated by reference in its entirety for allpurposes herein.

For example, one embodiment provides a composition comprising: at leastone hole transporting compound having a molecular weight of about 5,000or less, wherein the compound comprises at least one sulfur atom and atleast one oxygen atom, wherein the sulfur and oxygen atom are positionedin the compound so that a sulfur-oxygen intramolecular interaction ispresent. In one embodiment, the compound further comprises at least one,or at least two, or at least four crosslinking group. In one embodiment,the compound further comprises at least one crosslinking group, and thecompound is crosslinked. In one embodiment, the compound furthercomprises at least one crosslinking group which is a vinyl,perfluorocyclobutane, oxetane, silane, or benzocyclobutene group. In oneembodiment, the compound further comprises at least one crosslinkinggroup which comprises ethylenic unsaturation. In one embodiment, thecompound comprises at least one crosslinking group which is vinyl. Inone embodiment, the compound further comprises at least one crosslinkinggroup which comprises ethylenic unsaturation optionally linked to thecompound with a spacer group. In one embodiment, the compound furthercomprises at least one crosslinking group which comprises ethylenicunsaturation optionally linked to the compound with a spacer group,wherein the spacer group is —(CH₂)_(n)—, wherein n is 0-6. In oneembodiment, the compound further comprises at least one crosslinkinggroup which comprises ethylenic unsaturation linked to the compound witha spacer group, wherein the spacer group is —(CH₂)_(n)—, wherein n is1-6. In one embodiment, the compound comprises at least one, or at leasttwo, or at least four arylamine groups. In one embodiment, the compoundcomprises at least one arylamine group, wherein the arylamine groupcomprises a carbazole group. In one embodiment, the compound comprisesat least one arylamine group, wherein the arylamine group is a tertiaryarylamine. In one embodiment, the compound comprises at least one, or atleast two thiophene groups. In one embodiment, the compound comprises atleast one benzodithiophene group. In one embodiment, the compoundcomprises at least one benzo[1,2-b:4,5-b′]dithiophene group. In oneembodiment, the compound comprises at least two sulfur atoms, at leasttwo oxygen atoms, and at least two sulfur-oxygen interactions. In oneembodiment, the compound comprises at least one benzodithiophene groupwhich is substituted at the four and eight positions with an optionallysubstituted aryl ring. In one embodiment, the compound comprises atleast one benzodithiophene group which is substituted at the four andeight positions with an optionally substituted aryl ring comprising anoxygen-containing substituent. In one embodiment, the compound isrepresented by B1-A-B2, wherein B1 and B2 independently can be the sameor different. In one embodiment, the compound is represented by B1-A-B2,wherein B1 and B2 independently can be the same or different, and Acomprises at least one benzodithiophene group, and B1 and B2 eachcomprise at least one arylamine group. In one embodiment, the compoundis represented by B1-A-B2, wherein B1 and B2 independently can be thesame or different, and A comprises at least one benzodithiophene group,and B1 and B2 each comprise at least two arylamine groups. In oneembodiment, the compound is represented by B1-A-B2, wherein B1 and B2independently can be the same or different, and A comprises at least onebenzodithiophene group, and B1 and B2 each comprise at least twoarylamine groups, wherein B1 and B2 are linked to the benzodithiophenegroup at the 2 and 6 positions of the benzodithiophene group. In oneembodiment, the compound is represented by:

In one embodiment, the sulfur and the oxygen are linked by three carbonatoms. In one embodiment, the sulfur and the oxygen are linked by alinkage moiety comprising at least three carbon atoms including at leastone sigma bond. In one embodiment, the compound comprises at least 12,or at least 15, benzene rings. In one embodiment, the compound comprisesat least 12 benzene rings, at least two thiophene rings, and at leasttwo nitrogen atoms. In one embodiment, the compound comprises at least15 benzene rings, at least two thiophene rings, and at least fournitrogen atoms. In one embodiment, the compound is soluble in organicsolvent such as toluene. In one embodiment, the compound shows amobility of at least 10⁻⁵ cm²/Vs, or at least 10⁻⁴ cm²/Vs, or at least7.64×10⁻⁴ cm²/Vs, or the compound is soluble in organic solvent, and thecompound shows a mobility of at least 7.64×10⁻⁴ cm²/Vs. In oneembodiment, the sulfur-oxygen interaction can be detected by x-raydiffraction. In one embodiment, the sulfur-oxygen interaction can bedetected by an NMR method. In one embodiment, the composition furthercomprises at least one additional, different hole transporting compound.In one embodiment, the compound has a molecular weight of about 2,000 orless. In one embodiment, the compound has a molecular weight of about800 to about 2,000. In one embodiment, the compound has an ionizationpotential of about −5.2 eV to about −5.7 eV. In one embodiment, thecompound comprises at least one crosslinking group which has beencrosslinked, and the composition shows a 95% solvent wash resistance fortoluene. In one embodiment, the compound comprises a benzodithophenecore linked at the 2 and 6 positions to a hole transporting unit, eachunit comprising two arylamine groups, wherein each hole transportingunit is further functionalized with at least one crosslinking group. Inone embodiment, the compound comprises a benzodithophene core linked atthe 2 and 6 positions to a hole transporting unit, each unit comprisingat least one arylamine group, wherein the benzodithiophene isfunctionalized at the 4 and 8 positions with at least one crosslinkinggroup. In one embodiment, the compound comprises at least onecrosslinking group which has been crosslinked, at least four arylaminegroups, at least one benzodithiophene group, has a molecular weight ofabout 2,000 or less before crosslinking, is soluble in organic solventbefore crosslinking, and has a hole mobility of at least 10⁻⁴ cm²/Vsafter crosslinking.

Another embodiment provides a composition comprising: at least onecompound comprising at least one first thiophene ring moiety, and alsocomprising at least one first benzene ring moiety, wherein the firstthiophene ring moiety is covalently bonded to the first benzene ringmoiety at the 2 or 5 position of the thiophene ring to form a thiophenesubstituent for the first benzene ring moiety, and wherein the firstbenzene ring moiety comprises at least one oxygen atom ortho tothiophene ring substituent of the first benzene ring moiety, and furtherwherein the first benzene ring moiety is linked to at least onearylamine group.

Another embodiment provides a composition comprising: at least onearylamine hole transporting compound having a molecular weight of about5,000 or less, wherein the compound comprises at least one sulfur atomwhich is part of a thiophene ring, and at least one oxygen atom, whereinthe sulfur and oxygen atom are positioned in the compound so that asulfur-oxygen intramolecular interaction is present, wherein thecompound further comprises at least one crosslinking group.

Another embodiment provides a composition comprising: at least onearylamine compound comprising at least one first thiophene ring moiety,and also comprising at least one first benzene ring moiety, wherein thefirst thiophene ring moiety is covalently bonded to the first benzenering moiety at the 2 or 5 position of the thiophene ring to form athiophene substituent for the first benzene ring moiety, and wherein thefirst benzene ring moiety comprises at least one oxygen atom ortho tothiophene ring substituent of the first benzene ring moiety, and furtherwherein the first benzene ring moiety is linked to at least onearylamine group, and wherein the compound further comprises at least onecrosslinking group.

Another embodiment provides a composition prepared by crosslinking acomposition comprising at least one hole transporting compound having amolecular weight of about 5,000 or less, wherein the compound comprisesat least one sulfur atom and at least one oxygen atom, wherein thesulfur and oxygen atom are positioned in the compound so that asulfur-oxygen intramolecular interaction is present, wherein thecompound further comprises at least one crosslinking group.

Another embodiment provides a device comprising:at least one anode, atleast one cathode, at least one light emission layer, at least one holetransporting layer, wherein the hole transport layer comprises acomposition prepared by crosslinking a composition comprising at leastone hole transporting compound having a molecular weight of about 5,000or less, wherein the compound comprises at least one sulfur atom and atleast one oxygen atom, wherein the sulfur and oxygen atom are positionedin the compound so that a sulfur-oxygen intramolecular interaction ispresent, wherein the compound further comprises at least onecrosslinking group.

Another embodiment provides a coated substrate comprising a coatingcomposition prepared by crosslinking a composition comprising at leastone hole transporting compound having a molecular weight of about 5,000or less, wherein the compound comprises at least one sulfur atom and atleast one oxygen atom, wherein the sulfur and oxygen atom are positionedin the compound so that a sulfur-oxygen intramolecular interaction ispresent, wherein the compound further comprises at least onecrosslinking group. Another embodiment provides at least one compositioncomprising: at least one solvent, at least one hole transportingcompound having a molecular weight of about 5,000 or less, wherein thecompound comprises at least one sulfur atom and at least one oxygenatom, wherein the sulfur and oxygen atom are positioned in the compoundso that a sulfur-oxygen intramolecular interaction is present, whereinthe compound further comprises at least one crosslinking group. Anotherembodiment provides a method comprising: providing at least one inkcomposition comprising at least one solvent, and at least one holetransporting compound having a molecular weight of about 5,000 or less,wherein the compound comprises at least one sulfur atom and at least oneoxygen atom, wherein the sulfur and oxygen atom are positioned in thecompound so that a sulfur-oxygen intramolecular interaction is present,wherein the compound further comprises at least one crosslinking group;coating the composition onto a substrate, removing the at least onesolvent, crosslinking to provide a coated substrate.

Another embodiment provides a composition comprising at least one moietyrepresented by formula (I)

wherein the hole transporting units further comprise at least onecrosslinking group. In one embodiment, provided is a compositioncomprising a crosslinked form of the moiety represented by formula (I).

Another embodiment provides a composition comprising: at least one holetransporting compound having a molecular weight of about 5,000 or less,wherein the compound comprises at least two benzodithiophene moieties,and at least two fluorene moieties linked to the benzodithiophenemoieties, and wherein the compound comprises at least two sulfur atomsand at least two oxygen atoms, wherein the sulfur and oxygen atoms arepositioned in the compound so that a sulfur-oxygen intramolecularinteraction is present.

Methods of making these compounds are also described in the priorityprovisional application.

WORKING EXAMPLES

Additional embodiments are provided in the following working examples.

Working Example 1 Synthesis of PLX-D Synthesis of9,9-dioctyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine (1)

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 600 mL anhydrous toluene obtained from the solvent dispenser, 50.0g 9.9-dioctyl-2,7-dibromofluorene, and 23.7 mL m-toluidine. After thereaction mixture was degassed with strong nitrogen flow for 30 minutes,43.81 g sodium tert-butoxide, 3.34 gtris(dibenzylideneacetone)dipalladium(0) (Pd₂dba₃), and 2.22 gtri-tent-butyl phosphine in 30 mL anhydrous toluene were added. Thereaction mixture was heated to reflux. After three hours, the heatingwas turn off, and the reaction was allowed to cool down to roomtemperature. The reaction mixture was filtered through a Celite/silicagel plug. The product (51.9 g) was purified by flash chromatographyusing hexane, 1% then 3% ethyl acetate in hexane for first column, andusing the same eluents for second column. The structure was confirmed byNMR.

Synthesis of 2

Synthesis ofN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dioctyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine(2)

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 1000 mL anhydrous toluene obtained from the solvent dispenser,51.0 g 9,9-dioctyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine, and 38.3 mL2-(3-bromophenyl)-1,3-dioxolane. After the reaction mixture was degassedwith strong nitrogen flow for 30 minutes, 24.31 g sodium tert-butoxide,3.09 g tris(dibenzylideneacetone)dipalladium(0) (Pd₂dba₃), and 2.05 gtri-tent-butyl phosphine in 40 mL anhydrous toluene were added. Thereaction mixture was heated to reflux. After 2 hours, the heating wasturn off, and the reaction was allowed to cool down to room temperature.The reaction mixture was filtered through a Celite/silica gel plug. Theproduct (61.7 g) was purified by flash chromatography using hexane and5% ethyl acetate in hexane for first column, and using the same eluentsfor second column. The structure was confirmed by NMR.

Synthesis of 3

Dehalogenation ofN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dioctyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine

To a clean and dry round bottom flask under nitrogen, were added 60.0 gN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dioctyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine,1000 mL anhydrous THF, 92.79 mL triethylamine, and 25.12 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 1.49 g palladium (II) acetate and 2.02 g tri-tent-butylphosphine in 30 mL toluene were added. After the reaction was heated toreflux for 4 hours, the heat was removed and the reaction was allowed tocool down to room temperature. The reaction mixture was filtered througha Celite/silica gel plug, and the solvent was removed by evaporation.The crude product was dried under vacuum, and was carried on seconddehalogenation reaction without further purification.

To a clean and dry round bottom flask under nitrogen, were added 60.0 gN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dioctyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine,1000 mL anhydrous THF, 92.79 mL triethylamine, and 25.12 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 1.49 g palladium (II) acetate and 2.02 g tri-tent-butylphosphine in 30 mL toluene were added. After the reaction was heated toreflux for 4 hours, the heat was removed and the reaction was allowed tocool down to room temperature. The reaction mixture was filtered througha Celite/silica gel plug. The product (34.0 g) was purified by flashchromatography using hexane, 10% and 15% ethyl acetate in hexane. Thestructure was confirmed by NMR.

Synthesis of 4

Synthesis of3,3′-((9,9-dioctyl-9H-fluorene-2,7-diyl)bis(m-tolylazanediyl))dibenzaldehyde

To a three-neck round-bottom flask, were added 34.0 gN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dioctyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamineand in 1000 mL acetone. 189.5 mL 2 M hydrochloric acid solution wasadded slowly to the reaction mixture through an addition funnel. Thereaction was monitored by TLC. After the reaction was done showed byTLC, the solvent was removed by evaporation. 1000 mL Ethyl acetate wasadded, and the reaction mixture was extracted using DI water (3×750 mL).The combined organic layer was dried over magnesium sulfate. Afterfiltration, the solvent was removed by evaporation. The product (27.8 g)was obtained, and was carried on to next reaction without furtherpurification. The structure was confirmed by NMR.

Synthesis of 5 (PLX-D)

Synthesis of9,9-dioctyl-N2,N7-di-m-tolyl-N2,N7-bis(3-vinylphenyl)-9H-fluorene-2,7-diamine

To a oven-dried three-neck round-bottom flask under nitrogen, were added500 mL anhydrous THF, 11.95 g potassium tert-butoxide , and 36.82 gmethyltriphenylphosphonium bromide. The mixture was stirred for 30 min.27.8 g3,3′-((9,9-dioctyl-9H-fluorene-2,7-diyl)bis(m-tolylazanediyl))dibenzaldehydein 500 mL anhydrous THF was added through an additional funnel dropwiseto the reaction mixture over 30 min. After the reaction was stirred for2 hours, the reaction solution was filtered through a Celite/silica gelplug, and solvent was removed by evaporation. The product was firstpurified by flash chromatography using 100% hexane and then 1% ethylacetate in hexane. The structure was confirmed by NMR.

The further purification was performed by dissolving the column puresolid in minimal amount of HPLC acetone and then precipitating in HPLCMethanol, giving the final product (9.79 g). The structure was confirmedby NMR.

Working Example 2 Synthesis of PLX-I Synthesis of 6

Synthesis of 3-(4-bromobutyl)bicyclo[4.2.0]octa-1(6),2,4-triene

To an oven-dried three-neck round-bottom flask equipped with anadditional funnel and thermometer under nitrogen, were added 500 mLanhydrous THF and 25.0 g 4-bromobenzocyclobutane. The reaction mixturewas then cooled down to −73° C. in acetone/dry ice bath. 161 mLtert-Butyllithium (2M) was added drop by drop to the reaction throughthe addition, while keeping the reaction temperature below −65° C. Afteraddition of tert-butyl lithium, the dry ice/acetone bath was removed andthe reaction was allowed to warm up to −20° C., and then cooled down to−73° C. in dry ice/acetone bath. 65.7 mL 1,4-dibromobutane was addeddrop-wise via syringe, ensuring the reaction temperature stayed lowerthan −65° C. The reaction was allowed to slowly warm to room temperatureovernight. The reaction was quenched by the addition of isopropanol (25mL), and the solvent was removed by rotary evaporation. Ethyl acetate(500 mL) was added and then extracted with DI water (1000 mL×2) andbrine (200 mL×5). The combined organic layer was dried over anhydrousmagnesium sulfate, and the solvent was removed by evaporation. Theexcess starting material, 1,4-dibromobutane, was removed by vacuumdistilled at 90° C. Filtration through a Celite/silica gel plug afforded24.1 g NMR and GC-MS pure product.

Synthesis of 7

Synthesis of9-(4-(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)butyl)-9-(4-(bicyclo[4.2.0]octa-1,3,5-trien-3-yl)butyl)-2,7-dibromo-9H-fluorene

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 25.97 g of 2,7-dibromofluorene, 32.06 g sodium hydroxide, 1,33 gKI, and 300 mL anhydrous DMSO. The 46 g3-(4-bromobutyl)bicyclo[4.2.0]octa-1(6),2,4-triene 300 mL anhydrous DMSOwas added via cannula. The reaction was heated to 80° C. After 4 hours,the reaction was quenched by the addition of DI water (10 mL). Theexcess salt was removed by filtration. 500 mL Ethyl acetate was added,and extracted with DI water (3×300 mL) and brine (3×300 mL). Thecombined organic layer was dried over anhydrous magnesium sulfate.Magnesium sulfate was removed by filtration, and the solvent was removedby rotary evaporation. The product (43 g) was purified by flashchromatography using hexane. The structure was confirmed by NMR.

Synthesis of 8 (PLX-I)

Synthesis of9-(4-(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)butyl)-9-(4-(bicyclo[4.2.0]octa-1,3,5-trien-3-yl)butyl)-N2,N7-diphenyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 600 mL anhydrous toluene, 14.3 g9-(4-(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)butyl)-9-(4-(bicyclo[4.2.0]octa-1,3,5-trien-3-yl)butyl)-2,7-dibromo-9H-fluorene,and 9.2 mL 3-methyldiphenylamine. After the reaction mixture wasdegassed with strong nitrogen flow for 30 minutes, 6.44 g sodiumtert-butoxide, 0.82 g tris(dibenzylideneacetone)dipalladium(0)(Pd₂dba₃), and 0.54 g tri-tent-butyl phosphine in 15 mL toluene wereadded. The reaction mixture was heated to reflux. After three hours, theheating was turn off, and the reaction was allowed to cool down to roomtemperature. The reaction mixture was filter through a Celite/silica gelplug. The product (13.1 g) was purified by flash chromatography usinghexane, 1% then 5% ethyl acetate in hexane solution. The structure wasconfirmed by NMR.

Dehalogenation of9-(4-(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)butyl)-9-(4-(bicyclo[4.2.0]octa-1,3,5-trien-3-yl)butyl)-N2,N7-diphenyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine

To a clean and dry round bottom flask under nitrogen, were added 13.1 g9-(4-(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)butyl)-9-(4-(bicyclo[4.2.0]octa-1,3,5-trien-3-yl)butyl)-N2,N7-diphenyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine,500 mL anhydrous THF, 21.6 mL triethylamine, and 5.8 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 0.35 g palladium (II) acetate and 0.47 g tri-tent-butylphosphine in 15 mL toluene were added to reaction mixture. After thereaction was heated to reflux for 4 hours, the heat was removed and thereaction was allowed to cool down to room temperature. The reactionmixture was filter through a Celite/silica gel plug, and the solvent wasremoved by evaporator. The crude product was subjected to a seconddehalogenation without further purification.

To a clean and dry round bottom flask under nitrogen, were added 13.1 g9-(4-(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)butyl)-9-(4-(bicyclo[4.2.0]octa-1,3,5-trien)-3-yl)butyl)-N2,N7-diphenyl-N2,N7-di-m-tolyl-9H-fluorene-2,7-diamine,500 mL anhydrous THF, 21.6 mL triethylamine, and 5.8 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 0.35 g palladium (II) acetate and 0.47 g tri-tent-butylphosphine in 15 mL toluene were added to the reaction mixture. After thereaction was heated to reflux for 4 hours, the heat was removed and thereaction was allowed to cool down to room temperature. The reactionmixture was filter through a Celite/silica gel plug, and the solvent wasremoved by evaporator. The product was first purified by flashchromatography using hexane and 1% ethyl acetate in hexane. Thestructure was confirmed by NMR. The further purification was performedby dissolving the column pure solid in minimal amount of HPLC acetoneand then precipitating in HPLC Methanol, giving final product (12.38 g).The structure was confirmed by NMR.

Working Example 3 Synthesis of PLX-C Synthesis of 9

Synthesis of9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 1000 mL anhydrous toluene obtained from the solvent dispenser,50.05 g 2,7-dibromo-9,9-dimethyl-9H-fluorene, 48.89 gnaphthalen-1-amine. After the reaction mixture was degassed with strongnitrogen flow for 30 minutes, 41.02 g sodium tert-butoxide, 5.21 gtris(dibenzylideneacetone)dipalladium(0) (Pd₂dba₃), and 3.52 gtri-tent-butyl phosphine in 15 mL toluene were added. The reactionmixture was heated to reflux. After three hours, the heating was turnoff, and the reaction was allowed to cool down to room temperature. Thereaction mixture was filter through a Celite/silica gel plug. The crudeproduct was first purified by flash chromatography initially usinghexane, and 2.5% then 5% ethyl acetate in hexane. The final pure productwas purified by sublimation. The structure was confirmed by NMR.

Synthesis of 10

Synthesis ofN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 500 mL anhydrous dioxane, 5.8 g9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine, 5.9 mLof 2-(Bromophenyl)-1,3-dioxalane. After the reaction mixture wasdegassed with strong nitrogen flow for 30 minutes, 3.25 g sodiumtert-butoxide, 0.45 g tris(dibenzylideneacetone)dipalladium(0)(Pd₂dba₃), and 0.30 g tri-tent-butyl phosphine in 10 mL toluene wereadded. The reaction mixture was heated to reflux. After four hours, theheating was turn off, and the reaction was allowed to cool down to roomtemperature. The reaction mixture was filter through a Celite/silica gelplug. The product (4.1 g) was purified by flash chromatography initiallyusing hexane, and 10% then up to 30% ethyl acetate in hexane.

Synthesis of 11

Dehalo genation ofN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine

To a clean and dry round bottom flask under nitrogen, were added 8.0 gN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine,500 mL anhydrous THF, 14.43 mL triethylamine, and 3.91 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 0.232 g palladium (II) acetate and 0.314 g tri-tent-butylphosphine in 5 mL toluene were added. After the reaction was heated toreflux overnight, the heat was removed and the reaction was allowed tocool down to room temperature. The reaction mixture was filter through aCelite/silica gel plug, and the solvent was removed by evaporator. Thecrude product was carried on second dehalogenation without furtherpurification.

To a clean and dry round bottom flask under nitrogen, were added 8.0 gN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine,500 mL anhydrous THF, 14.43 mL triethylamine, and 3.91 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 0.232 g palladium (II) acetate and 0.314 g tri-tent-butylphosphine in 5 mL toluene were added. After the reaction was heated toreflux overnight, the heat was removed and the reaction was allowed tocool down to room temperature. The reaction mixture was filter through aCelite/silica gel plug, and the solvent was removed by evaporator. Thecrude product was carried on second dehalogenation without furtherpurification.

Synthesis of 12

Synthesis of3,3′-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(naphthalen-1-ylazanediyl))dibenzaldehyde

To a three-neck round-bottom flask, were added 8.0 gN2,N7-bis(3-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamineand in 100 mL acetone. 41.1 mL 2 M hydrochloric acid solution was addedslowly to the reaction mixture through an addition funnel. After TLCshowed the reaction was done, the solvent was removed by evaporation.200 mL Ethyl acetate was added, and the reaction mixture was extractedusing DI water (4×200 mL). The organic layer was dried over sodiumsulfate. After filtration, the solvent was removed by evaporation. Theproduct (6.9 g) was obtained after drying under vacuum, and was carriedon to next step without further purification. The structure wasconfirmed by NMR.

Synthesis of 13 (PLX-C)

Synthesis of9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-N2,N7-bis(3-vinylphenyl)-9H-fluorene-2,7-diamine

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 500 mL anhydrous THF, 3.51 g potassium tert-butoxide, and 10.80 gmethyltriphenylphosphonium bromide. The mixture was stirred for 10 min.6.9 g3,3′-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(naphthalen-1-ylazanediyl))dibenzaldehydein 250 mL anhydrous THF was added through an additional funnel dropwiseto the reaction mixture over 30 min. The reaction solution was filteredthrough a Celite/silica gel plug, and solvent was removed by rotaryevaporation. The product was first purified by flash chromatographyusing hexane and 1% ten 2% ethyl acetate in hexane. The structure wasconfirmed by NMR. The further purification was performed by dissolvingthe column pure solid in minimal amount of HPLC acetone and thenprecipitating in HPLC Methanol, giving final product (1.57 g). Thestructure was confirmed by NMR.

Example 4 Synthesis of PLX-B Synthesis of 14

Synthesis ofN2,N7-bis(4-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 700 mL anhydrous dioxane, 5.0 g9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine, and 4.8mL of 2-(4-bromophenyl)1,3-dioxalane. After the reaction mixture wasdegassed with strong nitrogen flow for 30 minutes, 3.05 g sodiumtert-butoxide, 0.38 g tris(dibenzylideneacetone)dipalladium(0)(Pd₂dba₃), and 0.26 g tri-tent-butyl phosphine in 10 mL toluene wereadded. The reaction mixture was heated to reflux. After four hours, theheating was turn off, and the reaction was allowed to cool down to roomtemperature. The reaction mixture was filtered through a Celite/silicagel plug. Purification by flash chromatography using hexane, and 5% thenup to 30% ethyl acetate in hexane afforded product (3.0 g) with 3 spotson TLC plate. NMR shows that they were the product and deprotectedaldehyde by-products. The following re-protected reaction was performed.To an oven-dried three-neck round-bottom flask equipped with Dean-Starkunder nitrogen, were added 250 mL toluene, 3.0 g column purifiedproducts, 4.6 mL of ethylene glycol, and 0.150 g of p-toluenesulfonicacid monohydrate. The reaction mixture was reflux, and the Dean Starktrap was drained as much as possible throughout the day but left fullovernight. After there was only single spot on TLC plate, the heatingwas turn off, and the reaction was allowed to cool down to roomtemperature. The reaction mixture was extracted with DI water (4×200mL), and the combined aqueous layer was extracted with methyl tert-butylether (2×200 mL). The combined organic layer was dried over sodiumsulfate. Sodium sulfate was removed by filtration, and solvent wasremoved by evaporation. The crude product was dissolved in 20 mL acetoneand precipitated into 500 mL MeOH. Solids was obtained by filtration anddried under vacuum, giving 2.42 g product. The structure was confirmedby NMR.

Synthesis of 15

Dehalogenation of9N2,N7-bis(4-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine

To a clean and dry round bottom flask under nitrogen, were added 2.4 gN2,N7-bis(4-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine,250 mL anhydrous THF, 4.36 mL triethylamine, and 1.18 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 0.07 g palladium (II) acetate and 0.095 g tri-tent-butylphosphine in 5 mL toluene were added. After the reaction was heated toreflux overnight, the heat was removed and the reaction was allowed tocool down to room temperature. The reaction mixture was filter through aCelite/silica gel plug, and the solvent was removed by evaporator. Thecrude product was carried on second dehalogenation without furtherpurification.

To a clean and dry round bottom flask under nitrogen, were added 2.4 gN2,N7-bis(4-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamine,250 mL anhydrous THF, 4.36 mL triethylamine, and 1.18 mL formic acid.After the reaction mixture was degassed with strong nitrogen flow for 30minutes, 0.07 g palladium (II) acetate and 0.095 g tri-tent-butylphosphine in 5 mL toluene. After the reaction was heated to refluxovernight, the heat was removed and the reaction was allowed to cooldown to room temperature. The reaction mixture was filter through aCelite/silica gel plug, and the solvent was removed by evaporator. Thecrude product was carried on to next deprotection reaction withoutfurther purification.

Synthesis of 16

Synthesis of4,4′-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(naphthalen-1-ylazanediyl)dibenzaldehyde

To a three-neck round-bottom flask, were added 2.42 gN2,N7-bis(4-(1,3-dioxolan-2-yl)phenyl)-9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-9H-fluorene-2,7-diamineand in 250 mL acetone. 20 mL 2 M hydrochloric acid solution was addedslowly to the reaction mixture through an addition funnel. After TLCshowed the reaction was done, the solvent was removed by evaporation.400 mL Ethyl acetate was added, and the reaction mixture was extractedusing DI water (4×200 mL). The organic layer was dried over sodiumsulfate. After filtration, the solvent was removed by evaporation. Theproduct (1.7 g) was purified by flash chromatography using hexane, and5% and up to 15% ethyl acetate in hexane. The structure was confirmed byNMR.

Synthesis of 17 (PLX-B)

Synthesis of9,9-dimethyl-N2,N7-di(naphthalen-1-yl)-N2,N7-bis(4-vinylphenyl)-9H-fluorene-2,7-diamine

To an oven-dried three-neck round-bottom flask under nitrogen, wereadded 175 mL anhydrous THF, 0.91 g potassium tert-butoxide, and 2.78 gmethyltriphenylphosphonium bromide. The mixture was stirred for 10 min.1.7 g4,4′-((9,9-dimethyl-9H-fluorene-2,7-diyl)bis(naphthalen-1-ylazanediyl))dibenzaldehydein 125 mL anhydrous THF was added through an additional funnel dropwiseto the reaction mixture over 30 min. The reaction solution was filteredthrough a Celite/silica gel plug, and solvent was removed by rotaryevaporation. The product (0.95 g) was purified by flash chromatographyusing 100% hexane and then 1% ethyl acetate in hexane. The structure wasconfirmed by NMR.

Example 5

Synthesis of 2-(3-(4-bromobutyl)phenyl)-1,3-dioxolane

To a clean and dry 2000 ml round bottom flask equipped with a 500 mladdition funnel, low temperature thermometer and magnetic stir bar wastransferred anhydrous tetrahydrofuran (800.0 ml) under nitrogen.2-(3-bromophenyl)-1,3-dioxolane (33.0 ml, 0.2183 mol) was added to thisflask by syringe. The reaction vessel was placed into a dry ice/acetonebath until a temperature of <−65° was achieved. The reaction mixture wasthen allowed to stir for 45 minutes at a stirring speed of 550 rpm inorder to verify the integrity of the stirring apparatus at thistemperature. Tert-butyllithium solution (257.0 ml, 0.4690 mol) wastransferred to the addition funnel by cannula, then added dropwise tothe reaction never allowing the temperature to rise above −65° C.Following addition, the reaction was allowed to stir for a period of 30minutes. The vessel was then removed from the dry ice/acetone bath andallowed to warm to a temperature of −20° C. The vessel was then againplaced into the dry ice/acetone bath until a temperature of <−65° wasachieved. 1,4-dibromobutane (103.5 ml, 0.8740 mol) was added to thereaction dropwise via syringe, maintaining the current temperature. Thereaction was allowed to stir for 30 minutes at this temperaturefollowing addition. The reaction was slowly warmed to room temperatureover the following 12 hours. After warming, the reaction was quenched bythe addition of isopropanol (20.0 ml) via syringe.

After quenching, solvent was removed by rotary evaporation using amaximum temperature of 70° C. Methyl tert-butyl ether (700.0 ml) wasadded and the solution was washed with deionized water (200.0 ml×8). Theorganic fraction was collected and dried over anhydrous sodium sulfate.Solids were then removed by vacuum filtration over a bed of Celite.Solvent was removed by rotary evaporation using a maximum temperature of70° C. The crude product was then purified by vacuum distillation at100° C. for 4 hours to remove most of 1,4-dibromobutane. Furtherpurification was carried out by automatic flash column chromatography onsilica gel using 3% ethyl acetate/97% hexane as an eluent. This providedpure product confirmed by NMR and GC-MS.

Synthesis ofN2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine

To a 2-liter three-neck round bottom flask was added anhydrous toluene(1000 mL) by cannula. 2,7-dibromofluorene (50.0 g) was added to thisflask, then stirred until all dissolved. N-phenyl-1-naphthylamine (81.14g) was then added. The reaction vessel was purged with a strong nitrogenflow for 30 minutes, followed by the addition of sodium tert-butoxide(44.5 g) by funnel. Tris(dibenzylideneacetone)dipalladium(0) (5.65 g)was added to the reaction. Tri-tert-butyl phosphine (3.75 g) inanhydrous toluene (20 mL) was added via syringe. The reaction was heatedto reflux for 2 hours and reaction completion was confirmed bythin-layer chromatography. The vessel was removed from heat and allowedto cool to room temperature. The reaction solution was filtered througha celite/silica gel plug and solvent was then removed by rotaryevaporation. The crude material was initially purified by flashchromatography, followed by sublimation to yield NMR pure product.

Synthesis of9,9-bis(4-(3-(1,3-dioxolan-2-yl)phenyl)butyl)-N2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine

A 1-liter three-neck round bottom flask equipped with a magnetic stirbar, high-temperature thermometer, and addition funnel was placed intoan inert atmosphere glovebox. This flask was charged with sodium hydride(0.63 g) and sealed with rubber septa. A solution ofN2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine (5.00g) in anhydrous N,N-dimethylformamide (DMF) (125 mL) was prepared in aninert atmosphere. At this point, all equipment was removed from theinert atmosphere glovebox. Attached a mineral oil bubbler to thereaction flask. The reaction vessel was then placed into a cool waterbath. TheN2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine/anhydrousDMF solution was then added to the reaction slowly dropwise via syringe.The reaction was allowed to stir in the water bath for 30 minutes. Thevessel was then removed from the bath and allowed to stir at roomtemperature for an additional 30 minutes. A solution of2-(3-(4-bromobutyl)phenyl)-1,3-dioxolane (5.71 g) in anhydrous DMF (15mL) was then prepared and added to the reaction dropwise via syringe.The reaction was allowed to stir at room temperature for 1 hour, thenplaced into an oil bath of 80 C for an additional 1 hour. Reactioncompletion was confirmed by thin-layer chromatography and was removedfrom heat. The reaction was quenched by slowly adding, portion-wise, toslightly iced DI water (400 mL) with vigorous stirring. Ethyl acetate(100 mL) was then added to this flask and stirred for 15 minutes. Thismixture was poured into a 2-liter reparatory funnel and another portionof ethyl acetate (100 mL) was added. The aqueous phase was extractedagain with ethyl acetate (350 mL) and all the organic fractions werecombined and washed with DI water (3×350 mL). The resulting organicfraction was dried with anhydrous sodium sulfate, and the solids wereremoved by gravity filtration. Silica gel was added to the resulting drysolution and solvent was removed by rotary evaporation leaving the crudematerial adsorbed to silica. Flash chromatography was carried out usingethyl acetate/hexane as a solvent system. Further purification byprecipitation from a minimum amount of acetone into cold methanol (2×950mL) yielded NMR pure product.

First dehalogenation of9,9-bis(4-(3-(1,3-dioxolan-2-yl)phenyl)butyl)-N2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine

A 1-liter three-neck round bottom flask was charged with9,9-bis(4-(3-(1,3-dioxolan-2-yl)phenyl)butyl)-N2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine(12.3 g). Anhydrous tetrahydrofuran (THF) (500 mL) was then added tothis flask. Triethylamine (17.0 mL) and formic acid (4.6 mL) were thenadded to the reaction via syringe. The reaction vessel was purged with astrong nitrogen flow for 30 minutes. Palladium (II) acetate (0.27 g) wasadded to the reaction. Tri-tert-butyl phosphine (0.36 g) in anhydroustoluene (10 mL) was then added by syringe and the reaction was heated toreflux. After 2 hours, the reaction was removed from heat and allowed tocool to room temperature. The reaction solution was filtered through acelite and silica gel plug. Solvent was removed by rotary evaporation.

Second dehalogenation of9,9-bis(4-(3-(1,3-dioxolan-2-yl)phenyl)butyl)-N2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine

A 1-liter three-neck round bottom flask was charged with9,9-bis(4-(3-(1,3-dioxolan-2-yl)phenyl)butyl)-N2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine(12.3 g). Anhydrous tetrahydrofuran (THF) (500 mL) was then added tothis flask. Triethylamine (17.0 mL) and formic acid (4.6 mL) were thenadded to the reaction via syringe. The reaction vessel was purged with astrong nitrogen flow for 30 minutes. Palladium (II) acetate (0.27 g) wasadded to the reaction. Tri-tert-butyl phosphine (0.36 g) in anhydroustoluene (10 mL) was then added by syringe and the reaction was heated toreflux. After 2 hours, the reaction was removed from heat and allowed tocool to room temperature. The reaction solution was filtered through acelite and silica gel plug. Solvent was removed by rotary evaporation.

Synthesis of3,3′-((2,7-bis(naphthalen-1-yl(phenyl)amino)-9H-fluorene-9,9-diyl)bis(butane-4,1-diyl))dibenzaldehyde

To 1-liter three-neck round bottom flask equipped with a magnetic stirbar and an addition funnel was transferred a solution of9,9-bis(4-(3-(1,3-dioxolan-2-yl)phenyl)butyl)-N2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9H-fluorene-2,7-diamine(12.3 g) in acetone (500 mL). Hydrochloric acid solution (61.0 mL, 2.0M)was transferred to the addition funnel atop the reaction flask bysyringe. The acid solution was added to the reaction dropwise withvigorous stirring. The reaction was allowed to stir for an additional 30minutes following the addition of acid. Reaction completion wasconfirmed by thin-layer chromatography and solvent was removed by rotaryevaporation. Ethyl acetate (750 mL) was added to the resulting mixtureand this solution was washed with DI water (5×200 mL). The organicfraction was collected and dried over anhydrous magnesium sulfate.Solids were removed by gravity filtration. Silica gel was added to thesolution and solvent was removed by rotary evaporation leaving the crudematerial adsorbed to silica. Crude product was initially purified byflash column chromatography using ethyl acetate/hexane as an eluent. Theresulting material was dissolved in a minimum amount of acetone andprecipitated into cold methanol (3×750 mL). The solids collected byvacuum filtration were dried and determined to be pure product by NMR.

Synthesis ofN2,N7-di(naphthalen-1-yl)-N2,N7-diphenyl-9,9-bis(4-(3-vinylphenyl)butyl)-9H-fluorene-2,7-diamine

To a 1-liter three-neck round-bottom flask under nitrogen, were addedanhydrous THF (400 mL), sodium tert-butoxide (2.69 g),methyltriphenylphosphonium bromide (8.28 g). The reaction mixture wasallowed to stir for 10 min. Then3,3′-((2,7-bis(naphthalen-1-yl(phenyl)amino)-9H-fluorene-9,9-diyl)bis(butane-4,1-diyl))dibenzaldehyde(7.12 g) in anhydrous THF (15 mL) was added dropwise through anadditional funnel. After 30 min, the reaction mixture was filteredthrough a Celite/Silica gel plug. The solvent was removed byevaporation. Purification by flash chromatography (1 - 3% ethyl acetatein hexane) afforded 6.8 g NMR pure product. The product was dissolved inHPLC grade acetone, and precipitation in MeOH gave final product (6.32g).

Example 6 Ink Formulation

Inks were formulated with a series of organic solvents used in lab celldevice fabrication including toluene, chlorobenzene, and o-xylene.Anhydrous solvent was purged with argon overnight to remove any residualoxygen present in the solvent; the purged solvent was then used for theformulation of the HTL ink. All the inks were formulated in the glovebox under nitrogen environment and stored in amber vials and anyexposure from light is avoided to prevent any kind of photo-degradationand photo-oxidation.

To formulate an ink called PLX-A, HTL materials PLX-D and PLX-I wereblended in the ratio 70: 30 by weight and dissolved in toluene at 1wt/wt % total solid content. Both molecules were weighed and mixed in avial, and the purged solvent was added thereafter. No heating wasrequired to dissolve the materials in the ink.

To formulate Ink B (below), materials PLX-D and PLX-B were blended in a90:10 by weight ratio and dissolved in toluene at 1 wt/wt % total solidscontent.

To formulate Ink C (below), materials PLX-L and PLX-B were blended in a50:50 by weight ratio and dissolved in toluene at 1 wt/wt % total solidscontent.

Example 7 Film Formation

An ink called PLX-N was prepared from PLX-D by thermally polymerizing insolution. A concentrated solution of the monomer was made at 30% wt.total solids in oxygen-free argon-purged toluene. The monomer solutionand stirbar were charged to a cleaned pressure reactor. The reaction washeated in a sandbath at 150-155° C. in a nitrogen glovebox. Heatedreaction for 13 hours at which time a gel had formed. Reaction wascooled and diluted to 1% total solids heated back to 80° C. to dissolveall solids. This solution was then filtered through a 1 um glass filterto provide a 0.32% total solids ink.

To study the film properties of aforementioned inks such as PLX-A, theink was pre-filtered using a 0.45 um PTFE filter and then dispensed ontothe substrate and spin coated on top of a hole injection layer.

Film Studies

-   The HOMO of PLX-A is -5.28 eV, and has about 100% film retain after    toluene wash.-   The HOMO of Ink B is -5.36 eV, and has about 100% film retain after    toluene wash.-   The HOMO of Ink C is -5.38 eV, and has about 100% film retain after    toluene wash.

HTL Characterization (PLX-A)

Parameter Units Value/Assessment HOMO (from AC2) eV 5.28 LUMO(calculation) eV 2.04 Band Gap (from eV 3.24 absorption spectrum) FilmSolvent % About zero (about Resistance to Toluene thickness change 100%film retained) Viscosity cP 0.67 cP @ 25° C.

Example 8 Ooptical Microscopy and Film Quality

For PLX-A, the optical microscopy images at 500× shows good film quality(FIG. 1), and the Root mean square roughness from AFM was 0.24 nm.

In contrast, when annealing small molecule HTL materials PLX-A on top ofNQ (NQ is non-aqueous) based HILs, beading up of the films was observed(FIG. 2).

While not being limited by theory, the problem may be dependent on theTg and lower molecular weight.

Example 9 Preopolymerization

The molecular weight of the material was increased via carrying out aprepolymerization reaction to offset the Tg and reduce the rate ofaggregate/bead formation. The prepolymerization was carried out viathree different approaches:

1) Thermal Pre Crosslinking

The HTL, PLX-D, was dissolved in oxygen-free argon-purged toluene athigher concentrations (30 wt/wt %) and then heated in a pressure reactorin a sand bath placed in a glove box to 150-155° C. until a gel wasformed. This gel was then redissolved in toluene to achieve the targetconcentration. With the increase in the molecular weight the beading upissue was succesfully resolved as shown in the micrograph of FIG. 3.

2) UV Precrosslinking on Ink

HTL compound W (structure above) was dissolved in oxgen free toluene toformulate the ink. After HTL ink was prepared, the ink was exposed to UVlight for partially cross-linking. After the UV exposure, the inkthickened and was diluted back to the target ink concentration toachieve the required film thickness. Then the ink was spun and anealedat 200° C. The optical microscopy at 500× image showed good film quality(FIG. 4). The same experiment was also tried with blends of Compound Wand PLX-D yielding similar results.

3) UV Precrosslinking on Film

HTL PLX-D was dissolved in oxygen free toluene to formulate the ink.After the HTL ink was spun on HIL, the film was annealed under UV andthen under thermal (200° C.) annealing. The optical microscopy at 500×image shows good film quality (FIG. 5).

Example 10 Meta Versus Para, PLX-B vs PLX-C

To investigate the reaction rates, i.e rate of crystallization (affinityfor the molecule to aggregate) as compared to the rate of crosslinking,and impact on morphology, film studies were carried out with PLX-C andPLX-B. The impact of meta versus para substitution was investigated.PLX-C (para) performed not as well as PLX-B (meta) (see FIGS. 6 and 7,respectively). Different substitution gave very different filmformation.

Example 11 Lifetime Testing

Compositions were prepared comprising mixtures of PLX-D and PLX-I. Theweight ratio of the two components was varied to determine impact onlifetime testing (see FIG. 8). The current formulation was selectedbased on screening of HTL ink formulation in PHOLED devices, therelative lifetime performance of the different blends is shown in Table2 and FIG. 9. (Accelerated LT80 testing: time required for the device todegrade to 80% of its luminance value). The reference HTL on this scaleis at 0.7. The 70:30 ratio provided the best lifetime for the device inthis study.

TABLE 2 Annealing T Inks* (° C.) Film Formation INK A 250 AQ INK B 200AQ/NQ INK C 200 AQ/NQ *Structures described further below In Table 2,Ink A comprises:

Ink B comprises:

Ink C comprises:

Example 12 Stability Testing as Measured by TLC

The relative stability of compounds PLX-D and PLX-I was measured by TLCmeasurements. Solid samples were store in a glovebox in amber vials forsix weeks (compound PLX-D) and seven weeks (PLX-I). A TLC single spotindicated there was only product, with no decomposition. If there weremultiple spots, it indicated there was decomposition. Compound PLX-Dshowed two spots (less stability). Compound PLX-I showed one spot (morestability).

Additional Syntheses: Example 13 Synthesis of Core

Synthesis of 4,8-di-m-tolylbenzo[1,2-b:4,5-b′]dithiophene

A clean and dry 2000 ml round bottom flask equipped with refluxcondenser, magnetic stir bar, and thermometer with adapter was prepared,purged, and then charged with4,8-dihydrobenzo[1,2-b:4,5-b′]dithiophen-4,8-dione (7.34 g, 0.0333 mol)Anhydrous tetrahydrofuran (900.0 ml) was then added to this flask bycannula and stirring was initiated. Heat was applied to the reactionvessel to dissolve this material. The reaction vessel was placed into awater bath and m-tolylmagnesium bromide solution (100 ml, 0.1000 mol)was added via cannula. Following addition, the vessel was removed fromthe water bath and heated to reflux for 1 hour. The reaction was thenremoved from heat and allowed to cool to room temperature.m-tolylmagnesium bromide solution (100 ml, 0.1000 mol) was added viacannula and the reaction was again heated to reflux for 1 hour. Theprogress of the reaction was monitored by GC-MS and no starting materialwas present. The reaction was subsequently removed from heat and cool toroom temperature overnight. A hydrochloric acid (160.0 ml, 10%)/tin (II)chloride (30.05 g, 0.1333 mol) solution was then prepared and added tothe reaction via syringe. The reaction vessel was again heated to refluxfor 1 hour, then removed from heat and allowed to cool to roomtemperature. Solvent was removed by rotary evaporation. Ethyl acetate(500.0 ml) was and the crude mixture was nearly dissolved. The volumewas washed once with DI H₂O (500 mL), and the organic layer containingsolids was collected. Solids were removed by vacuum filtration,collected, and washed in hot methanol. The filtrate was dried overanhydrous magnesium sulfate, filtered, and removed of solvent by rotaryevaporation. To the remaining crude material acetone (25.0 ml) andmethanol (500.0 ml) were added and heated to reflux in trituration for 1hour. The resulting solids in solution were vacuum-filtered andcollected. All solids collected during purification were proved to bepure by NMR spectroscopy.

Synthesis of 2,6-dibromo-4,8-di-m-tolylbenzo[1,2-b:4,5-b′]dithiophene

A 1000 ml round bottom flask equipped with an addition funnel, magneticstir bar, and low-temperature thermometer with adapter was charged with4,8-di-m-tolylbenzo[1,2-b:4,5-b′]dithiophene (TH-1-180, 4.50 g, 0.0121mol). Anhydrous tetrahydrofuran (300.0 ml) was then added to this flaskvia cannula while stirring. It is important to note that the solubilityof this starting material is very poor in tetrahydrofuran. The reactionvessel was heated by heat gun, with vigorous stirring until all4,8-di-m-tolylbenzo[1,2-b:4,5-b′]dithiophene dissolved. The reaction wasplaced into a dry ice/acetone bath until a temperature of less than −70°C. was achieved. Tert-butyllithium solution (19.5 ml, 0.0330 mol) wastransferred to the addition funnel by syringe and added to the reactiondropwise. The temperature was monitored as not to allow it to warm togreater than −68° C. Following addition, the reaction was allowed tostir for 30 minutes at this temperature. The reaction was removed fromthe dry ice/acetone bath and allowed to warm to a temperature of above5° C. The reaction was again placed into a dry ice/acetone bath until atemperature of less than −70° C. was reached. Dibromotetrafluoroethane(12.6 g, 0.0486 mol) was added to the reaction dropwise via syringe, andallowed to stir for 30 minutes. The reaction vessel was removed from thedry ice/acetone bath and allowed to warm to room temperature slowly overthe weekend. TLC was used to confirm reaction completion. The reactionwas then quenched by the addition of DI H₂O (20.0 ml) via syringe.Solvent was removed by rotary evaporation. The resulting crude materialwas dissolved in hot chloroform (500.0 ml) and washed with DI H₂O(1×300.0 ml). The organic fraction was collected and dried overanhydrous magnesium sulfate. Solids were removed by filtration andsolvent by rotary evaporation. A solution of 1:1 methanol/DI H₂O (300.0ml) was added to the crude product and heated to reflux in triturationfor 45 minutes. The flask was allowed to cool, and the solids werevacuum filtered. Methanol (250.0 ml) was added to the crude solids andagain heated to reflux in trituration with vigorous stirring for 1 hour.The solids were vacuum filtered from the hot methanol solution and driedunder vacuum. This resulted in pure product confirmed by GC-MS and NMR.

Example 14 Synthesis of Core

Synthesis of2,6-dibromo-4,8-bis(3-ethylheptyl)benzo[1,2-b:4,5-b′]dithiophene

A dry three-neck flask was flushed with nitrogen and was charged with4,8-bis(3-ethylheptyl)benzo[1,2-b:4,5-b′]dithiophene (30.7 g, 0.0693mol) and diethyl ether (Et₂O) (700 mL, 0.1 M) via cannula. The reactionflask was cooled to −78° C. and a 1.3 M solution of tert-butyllithium inhexanes (144 mL, 0.187 mol) was added dropwise via deoxygenated syringe.After 30 minutes of stirring at −78° C., the solution was warmed up to5° C. and stirring was continued for 5 minutes, at which point thereaction mixture was chilled back to −78° C. Dibromotetrafluoroethane(33 mL, 0.277 mol) was added to the reaction flask dropwise and stirringcontinued for 1 hours at −78° C. The cooling bath was removed and thereaction mixture was allowed to warm to ambient temperature. As thereaction was completed, cool DI water (20 mL) was slowly added to thereaction flask. Then, the reaction mixture was poured into cool DI waterand extracted with methyl tert-butyl ether three times. The combinedorganic layer was washed with water two times and dried over anhydrousmagnesium sulfate (MgSO₄). After the product was filtered, the solventwas removed by rotary evaporation. The crude product was dissolved intetrahydrofuran and precipitated into cold methanol. The precipitate wasobtained by filtration to yield pure product. Additional amounts ofproduct can be recovered from concentrating down themethanol/tetrahydrofuran filtrate.

Example 15 Core Synthesis

Synthesis of2,2′-((9,10-dioxo-9,10-dihydroanthracene-1,5-diyl)bis(sulfanediyl))diaceticacid

Anhydrous ethanol (2000.0 ml) was added to a 5000 ml three-neck roundbottom flask equipped with a reflux condenser, mechanical stirrer, and athermometer with adapter. Sodium (24 g, 1.0439 mol) was slowly added insmall pieces over a 1.5 to 2 hour period. Then,1,5-dichloroanthracene-9,10-dione (45.6 g, 0.1646 mol), 2-mercaptoaceticacid (25.6 ml, 0.3668 mol), manganese dioxide (8 g, 0.0920 mol), and15-crown-5 (0.8 g, 0.0036 mol) were added into the reaction. The mixturewas heated under nitrogen at 70° C. for 10 hours. After cooling to roomtemperature, DI H₂O (1500 ml) was added to the suspension whilestirring. The resulting solution was filtered and 2.0 N HCl was added tothe filtrate to generate a yellow precipitate. The yellow solid wascollected by centrifuge, washed with DI H₂O three times and then driedin the oven to give 54 g of product (84% yield).

Synthesis of anthra[1,9-bc:5,10-b′c′]dithiophene

Finely ground2,2′-((9,10-dioxo-9,10-dihydroanthracene-1,5-diyl)bis(sulfanediyl))diaceticacid (120 g, 0.3090 mol) was slowly added to dry acetic anhydride (1800ml) in a 3000 ml three-neck round bottom flask equipped with a refluxcondenser. The reaction was refluxed for 4 hours under nitrogen untilthe evolving fine stream of gas completely ceased. The reaction wascooled down to room temperature to give black crude product. The blackcrude product was isolated and sublimed under vacuum to give the pureproduct 57.7 g (71% yield).

Synthesis of 1,6-dibromoanthra[1,9-bc:5,10-b′c′]dithiophene

anthra[1,9-bc:5,10-b′c′]dithiophene (18 g, 0.0681 mol) was added toanhydrous DMF (1125 ml) in a 2000 ml three-neck round bottom flask. Thesuspension was heated to 140° C. under a nitrogen flow until allstarting material was completely dissolved. The solution was cooled downto approximately 60° C. N-Bromosuccinimide (30.3 g, 0.1702 mol) inanhydrous DMF (191 ml) was slowly added into the reaction flask. Theproduct immediately precipitated out. The mixture was heated toapproximately 80° C. for 1 hour with vigorous stirring. After cooling,the precipitates were filtered, washed with acetone, and dried to give27.44 g of product (95% yield).

Example 16 Core Synthesis

Synthesis of 4,8-bis(3-ethylhept-1-ynyl)thieno[2,3-f]benzothiophene

A dry 500-mL three-neck flask with an attached reflux condenser wasflushed with N₂ and was charged with 3-ethylhept-1-yne (10.5 g, 0.084mol) and THF (200 mL, 0.4 M) via deoxygenated syringe. The reactionflask was cooled to 0° C. and a 2.5 M solution of n-butyllithium inhexanes (32.2 mL, 0.080 mol) was added dropwise via deoxygenatedsyringe. After 30 minutes of stirring at 0° C., the solution was warmedto ambient temperature and benzo[1,2-b:4,5-b′]dithiophene-4,8-dione(4.43 g, 0.02 mol) was added portion-wise. The reaction was stirred atambient temperature for 3 days. As the reaction was completed, cool DIwater (3 mL) was slowly added to the reaction flask. A solution of SnCl₂(3 g) dissolved in 10% HCl (10 mL) was added to the reaction andstirred, increasing temperature to reflux for 1 hour and then coolingthe reaction to ambient temperature. The reaction was poured into 200 mLof cool water with 10 mL of 10% HCl and extracted with hexanes (300 mL)three times. The combined organic layer was dried over anhydrousmagnesium sulfate (MgSO₄). After the product was filtered, the solventwas removed by rotary evaporation. The product was purified using columnchromatography on silica gel with hexanes/chloroform (gradient) to yielda colorless oil (3.0 g, 35%).

Synthesis of 4,8-bis(3-ethyl)thieno[2,3-f]benzothiophene

A dry 250 mL 1-neck flask was flushed with N₂ and was charged with4,8-bis(3-ethylhept-1-ynyl)thieno[2,3-f]benzothiophene (3.04 g, 0.007mol), Pd/C wet support (0.82 g, 10%) and THF (15 mL, 0.5 M). The flaskwas evacuated and backfilled with hydrogen. The flask was kept under ahydrogen atmosphere and was monitored by TLC. After the reaction wascompleted, the mixture was filtered through Celite and solvent wasremoved by rotary evaporation.

Example 17 Core Synthesis

The synthesis of this compound is described in US Patent Publication No.2011/0028644 (assignee: Plextronics, Inc.).

Example 18 Core Synthesis

The moiety below comprising three thiophenes fused to a central phenylring can be used as a core to prepare arylamine hole transportingcompounds. A synthesis strategy is described in US Patent Publication2011/0028644.

Example 19 Arylamine, Stabilizing Group Synthesis

Synthesis of N-(3-(1,3-dioxolan-2-yl)phenyl)-3-methylaniline

To a clean and dry 500 ml round bottom flask equipped with a refluxcondenser and magnetic stir bar nitrogen was purged and anhydroustoluene (250.0 ml) was added by cannula. m-toluidine (5.1 ml, 0.0467mol) was added to the reaction flask by syringe. Next,2-(3-bromophenyl)-1,3-dioxolane (7.8 ml, 0.0513 mol) was added bysyringe. The reaction solution was purged with a strong nitrogen flowfor 30 minutes. Sodium tert-butoxide (6.73 g, 0.0701 mol) and Pd2dba3(0.85 g, 0.0009 mol) were then added manually, followed by the additionof tri-tent-butylphosphine (0.57 g, 0.0028 mol) in toluene (˜8 ml) viasyringe. The vessel was heated to reflux for approximately 4 hours. Thereaction was then cooled to room temperature and filtered through aCelite and silica gel pad. Solvent was removed by rotary evaporation.The crude material was partially dissolved in a 10% ethyl acetate/hexanesolution (20.0 ml) and purified by flash column chromatography providingnear pure product. Further purification was carried out using anautomatic column chromatography system using 5% ethyl acetate/hexane asan eluent. This provided pure product confirmed by NMR.

Example 20 Arylamine, Stabilizing Group Synthesis

Synthesis of N-(3-(1,3-dioxolan-2-yl)phenyl)dibenzo[b,d]thiophen-4-amine

A clean and dry 1000 ml round bottom flask equipped with a refluxcondenser, magnetic stir bar, and thermometer with adapter was preparedand purged with nitrogen. A solution of 4-bromodibenzo[b,d]thiophene(RS-1-170, 10.7 g, 0.0407 mol) in anhydrous toluene (500.0 ml) was thenprepared and transferred to the reaction flask via cannula.3-aminobenzaldehyde ethylene acetal (8.1 g, 0.0488 mol) was added bysyringe. The reaction solution was purged with a strong nitrogen flowfor 20 minutes. Sodium tert-butoxide (5.86 g, 0.0610 mol) and Pd2dba3(1.10 g, 0.0012 mol) were then added manually, followed by the additionof tri-tert-butylphosphine (0.65 g, 0.0032 mol) in toluene (-10 ml) viasyringe. The vessel was heated to reflux for approximately 2 hours. Thereaction was then cooled to room temperature and filtered through aCelite and silica gel pad. Solvent was removed by rotary evaporation.The crude material was dissolved in a 2:1 hexane/ethyl acetate solutionpurified by flash column chromatography using a gradient elution systemof ethyl acetate/hexane. This provided pure product confirmed by NMR.

Example 21 Arylamine, Stabilizing Group Synthesis

Synthesis of N-(3-(1,3-dioxolan-2-yl)phenyl)naphthalen-1-amine

A clean and dry 500 ml round bottom flask equipped with a refluxcondenser, magnetic stir bar, and thermometer with adapter was preparedand purged with nitrogen Anhydrous toluene (250.0 ml) was transferred tothis flask by cannula. 2-(3-bromophenyl)-1,3-dioxolane (6.0 ml, 0.0397mol) was added by syringe followed by the manual addition of1-naphthylamine (5.08 g, 0.0355 mol). The reaction solution was purgedwith a strong nitrogen flow for 30 minutes. Sodium tert-butoxide (5.60g, 0.0583 mol) and Pd2dba3 (0.65 g, 0.0007 mol) were then addedmanually, followed by the addition of tri-tert-butylphosphine (1.30 g,0.0064 mol) in toluene (-10 ml) via syringe. The vessel was heated toreflux for approximately 5 hours. The reaction was then cooled to roomtemperature and filtered through a Celite and silica gel pad washingthoroughly with acetone and chloroform. Solvent was removed by rotaryevaporation. The crude material was purified by flash columnchromatography using ethyl acetate/hexane as an eluent. This providedpure product confirmed by NMR spectroscopy.

Example 22 Intermediate

Synthesis of 2-(3-(4-bromobutyl)phenyl)-1,3-dioxolane

To a clean and dry 2000 ml round bottom flask equipped with a 500 mladdition funnel, low temperature thermometer and magnetic stir bar wastransferred anhydrous tetrahydrofuran (800.0 ml) under nitrogen.2-(3-bromophenyl)-1,3-dioxolane (33.0 ml, 0.2183 mol) was added to thisflask by syringe. The reaction vessel was placed into a dry ice/acetonebath until a temperature of <−65° was achieved. The reaction mixture wasthen allowed to stir for 45 minutes at a stirring speed of 550 rpm inorder to verify the integrity of the stirring apparatus at thistemperature. Tert-butyllithium solution (257.0 ml, 0.4690 mol) wastransferred to the addition funnel by cannula, then added drop wise tothe reaction never allowing the temperature to rise above −65° C.Following addition, the reaction was allowed to stir for a period of 30minutes. The vessel was then removed from the dry ice/acetone bath andallowed to warm to a temperature of −20° C. The vessel was then againplaced into the dry ice/acetone bath until a temperature of <−65° wasachieved. 1,4-dibromobutane (103.5 ml, 0.8740 mol) was added to thereaction dropwise via syringe, maintaining the current temperature. Thereaction was allowed to stir for 30 minutes at this temperaturefollowing addition. The reaction was slowly warmed to room temperatureover the following 12 hours. After warming, the reaction was quenched bythe addition of isopropanol (20.0 ml) via syringe.

After quenching, solvent was removed by rotary evaporation using amaximum temperature of 70° C. Methyl tert-butyl ether (700.0 ml) wasadded and the solution was washed with deionized water (200.0 ml×8). Theorganic fraction was collected and dried over anhydrous sodium sulfate.Solids were then removed by vacuum filtration over a bed of Celite.Solvent was removed by rotary evaporation using a maximum temperature of70° C. The crude product was then purified by vacuum distillation at100° C. for 4 hours to remove most of 1,4-dibromobutane. Furtherpurification was carried out by automatic flash column chromatography onsilica gel using 3% ethyl acetate/97% hexane as an eluent. This providedpure product confirmed by NMR and GC-MS.

Example 23 Intermediate-2

Synthesis of 3-(4-bromobutyl)bicyclo[4.2.0]octa-1(6),2,4-triene

To a clean and dry 1000 ml round bottom flask equipped with a 250 mladdition funnel, low temperature thermometer and magnetic stir bar wastransferred anhydrous tetrahydrofuran (500.0 ml) under nitrogen.4-bromobenzocyclobutane (25.0 g, 0.1370 mol) was added to this flask bysyringe. The reaction vessel was placed into a dry ice/acetone bathuntil a temperature of <−70° C. was achieved. The reaction mixture wasthen allowed to stir for 45 minutes at a stirring speed of 550 rpm inorder to verify the integrity of the stirring apparatus at thistemperature. Tert-butyllithium solution (161 ml, 0.2730 mol) wastransferred to the addition funnel by cannula, then added dropwise tothe reaction never allowing the temperature to rise above −65° C.Following addition, the reaction was allowed to stir for a period of 30minutes. The vessel was then removed from the dry ice/acetone bath andallowed to warm to a temperature of −20° C. The vessel was then againplaced into the dry ice/acetone bath until a temperature of <−70° wasachieved. 1,4-dibromobutane (64.7 ml, 0.5460 mol) was added to thereaction dropwise via syringe, maintaining the current temperature. Thereaction was allowed to stir for 30 minutes at this temperaturefollowing addition. The reaction was slowly warmed to room temperatureover the following 12 hours. Reaction completion was confirmed by GC-MS.After warming, the reaction was quenched by the addition of isopropanol(25.0 ml) via syringe.

After quenching, solvent was removed by rotary evaporation. Ethylacetate (500 ml) was added and the solution was washed with DIwater/brine (1000 ml×2, 200 ml×5). The organic fraction was collectedand dried over anhydrous magnesium sulfate. Solids were then removed bygravity filtration and solvent was removed by rotary evaporation. Thecrude product was then purified by vacuum distillation at a temperatureof 90° C. for 4 hours to remove excess 1,4-dibromobutane. This providedpure product confirmed by NMR and GC-MS.

Comparative Example A

Polymers with similar cross linking functionality were used as a blenderin the HTL formulation to increase the overall molecule weight and alsoact as a spacer between small molecule hence, in an attempt to preventthe formation of bead like structures in the HTL. However, these filmsshowed anywhere between 5-20% film loss with toluene wash.

1. A composition comprising: at least one first compound and at least one second compound different from the first, wherein the at least one first compound comprises a hole transporting core which is a fluorene core, wherein the hole transporting core is covalently bonded to a first arylamine group and also covalently bonded to a second arylamine group, and wherein the core is further covalently bonded to at least two solubilizing groups comprising at least four carbon atoms, and wherein the solubilizing groups are optionally substituted with intractability groups; wherein the at least one second compound comprises a hole transporting core which is a fluorene core, wherein the hole transporting core is covalently bonded to a first arylamine group and also covalently bonded to a second arylamine group, wherein the second compound further comprises at least one intractability group which may be bonded to the first arylamine group, the second arylamine group, or both; wherein the first and second compounds have molecular weight of about 5,000 g/mole or less.
 2. The composition of claim 1, wherein the relative amounts of the first and second compounds are about 99:1 to about 1:99 by weight, respectively.
 3. The composition of claim 1, wherein the relative amounts of the first and second compounds are about 90:1 to about 10:90 by weight, respectively.
 4. The composition of claim 1, wherein the relative amounts of the first and second compounds are about 20:80 to about 40:60 by weight, respectively.
 5. The composition of claim 1, wherein the relative amounts of the first and second compounds are about 99:1 to about 80:20 by weight, respectively.
 6. The composition of claim 1, wherein the relative amounts of the first and second compounds are about 40:60 to about 60:40 by weight, respectively.
 7. The composition of claim 1, wherein the molecular weight of the first compound is about 2,000 or less, and the molecular weight of the second compound is about 2,000 or less.
 8. The composition of claim 1, wherein the molecular weight of the first compound is about 1,000 or less, and the molecular weight of the second compound is about 1,000 or less.
 9. The composition of claim 1, wherein the first compound has only two arylamine groups, and the second compound has only two arylamine groups.
 10. The composition of claim 1, wherein the core fluorene group of the first and second compounds are bonded to the arylamines at the 2 and 7 positions of the fluorene group and the core fluorene group is bonded to the solubilizing groups at the 9 position.
 11. The composition of claim 1, wherein for the first compound the two solubilizing groups each comprise at least eight carbon atoms.
 12. The composition of claim 1, wherein the second compound comprises at least one intractability group which is bonded to the first arylamine group, and at least one intractability group which is bonded to the second arylamine group.
 13. The composition of claim 1, wherein the intractability group for the second compound is vinyl.
 14. The composition of claim 1, wherein the intractability group for the second compound is vinyl which is covalently bonded to a phenyl ring to form a styrene unit.
 15. The composition of claim 1, wherein for the first and second compounds, the first and send arylamine groups are the same group.
 16. The composition of claim 1, wherein the two solubilizing groups bonded to the fluorene core are the same groups.
 17. The composition of claim 1, wherein at least one of the arylamine groups comprises an optionally substituted naphthyl group bonded to nitrogen.
 18. The composition of claim 1, wherein at least one of the arylamine groups comprises an both an optionally substituted naphthyl group and an optionally substituted phenyl group bonded to nitrogen.
 19. The composition of claim 1, wherein the first and second compounds have a solubility of at least 5 wt. %.
 20. The composition of claim 1, wherein the intractable groups are polymerizable groups.
 21. The composition of claim 1, wherein for the first compound, the solubilizing group is substituted with the intractability group, and for the second compound the core further comprises at least two solublizing groups comprising at least four carbon atoms.
 22. The composition of claim 21, wherein the relative amounts of the first and second compounds are about 20:80 to about 40:60 by weight, respectively.
 23. The composition of claim 21, wherein the relative amounts of the first and second compounds are about 25:75 to about 35:65 by weight, respectively.
 24. The composition of claim 21, wherein for the first compound the intractability group is benzocyclobutane.
 25. The composition of claim 21, wherein for the second compound the core further comprises at least two solublizing groups comprising at least eight carbon atoms.
 26. The composition of claim 21, wherein for the second compound the solubilizing groups do not comprise intractability groups.
 27. The composition of claim 21, wherein the first compound and the second compound comprise different intractability groups.
 28. The composition of claim 21, wherein the first compound is represented by:


29. The composition of claim 21, wherein the second compound is represented by:


30. The composition of claim 21, wherein the first compound is represented by

and the second compound is represented by:


31. The composition of claim 1, wherein for the first compound, the solubilizing group of the core is unsubstituted with intractability group.
 32. The composition of claim 31, wherein the relative amounts of the first and second compounds are about 99:1 to about 80:20 by weight, respectively.
 33. The composition of claim 31, wherein the relative amounts of the first and second compounds are about 95:5 to about 85:15 by weight, respectively.
 34. The composition of claim 31, wherein for the first compound the intractability group is on at least one of the arylamine groups and is vinyl
 35. The composition of claim 31, wherein for the second compound the core further comprises to groups bonded to fluorene which are C3, C2, or C1 groups.
 36. The composition of claim 31, wherein for the second compound intractability groups bonded to the first and second arylamine which are vinyl bonded to phenyl to form a para-styrene.
 37. The composition of claim 31, wherein the first compound does not comprise intractability groups bonded to the core.
 38. The composition of claim 31, wherein the first compound is represented by:


39. The composition of claim 31, wherein the second compound is represented by:


40. The composition of claim 31, wherein the first compound is represented by:

and the second compound is represented by:


41. The composition of claim 1, wherein for the first compound, the solublizing group is substituted with the intractability group and the for the second compound, the core does not comprise at least two solublizing groups comprising at least four carbon atoms.
 42. The composition of claim 41, wherein the relative amounts of the first and second compounds are about 80:20 to about 20:80 by weight, respectively.
 43. The composition of claim 41, wherein the relative amounts of the first and second compounds are about 60:40 to about 40:60 by weight, respectively.
 44. The composition of claim 41, wherein for the first compound the intractability group is vinyl.
 45. The composition of claim 41, wherein for the first compound the intractability group is vinyl bonded to a phenyl to form a styrene unit.
 46. The composition of claim 41, wherein for the second compound the core further comprises to groups bonded to fluorene which are C3, C2, or C1 groups.
 47. The composition of claim 41, wherein for the second compound intractability groups bonded to the first and second arylamine which are vinyl bonded to phenyl to form a para-styrene.
 48. The composition of claim 41, wherein the first compound is represented by:


49. The composition of claim 41, wherein the second compound is represented by:


50. The composition of claim 41, wherein the first compound is represented by:

and the second compound is represented by:


51. The composition of claim 1, wherein the composition further comprises a solvent system to form an ink.
 52. The composition of claim 1, wherein the composition further comprises a solvent system to form an ink, wherein the solid content of the ink is about 0.5 to about 5 wt/wt % total solids.
 53. The composition of claim 1, wherein the composition further comprises a solvent system to form an ink, and the solvent system comprises toluene, o-xylene, chlorobenze, or mixtures thereof as solvent.
 54. The composition of claim 1, wherein the intractable groups are polymerizable groups, and the polymerizable groups are reacted.
 55. A composition prepared by reaction of the first and second compounds of the composition of claim
 1. 56. The composition of claim 1, wherein the composition further comprises at least one third compound, different from the first and second compounds, which activates a polymerization reaction for the composition.
 57. The composition of claim 1, wherein the composition further comprises at least one third compound, different from the first and second compounds, which comprises para-styrene units.
 58. The composition of claim 1, wherein the composition further comprises at least one third arylamine compound, different from the first and second arylamine compounds, wherein the third arylamine compound has only one crosslinking group.
 59. The composition of claim 1, wherein the composition further comprises at least one third arylamine compound, different from the first and second arylamine compounds, wherein the third arylamine compound has three or more crosslinking groups.
 60. The composition of claim 1, wherein the composition further comprises at least one third arylamine compound, wherein the third arylamine compound has a lower LUMO and lower or similar HOMO compared to the first and second compounds.
 61. A composition comprising: at least one compound comprising a hole transporting core, wherein the core is covalently bonded to a first arylamine group and also covalently bonded to a second arylamine group, and wherein the compound is covalently bonded to at least one intractability group, wherein the intractability group is covalently bonded to the hole transporting core, the first arylamine group, the second arylamine group, or a combination thereof, and wherein the compound has a molecular weight of about 5,000 g/mole or less.
 62. The composition of claim 61, wherein the compound comprises at least three intractability groups, and at least one intractability group is covalently bonded to the hole transport core, and at least one intractability group is covalently bonded to the first arylamine group, and at least one intractability group is covalently bonded to the second arylamine group.
 63. The composition of claim 61, wherein the intractability group is covalently bonded to the hole transport core but not the first arylamine group or the second arylamine group.
 64. The composition of claim 61, wherein the intractability group is covalently bonded to the first arylamine group, the second arylamine group, or both, but is not bonded to the hole transport core.
 65. The composition of claim 61, wherein the compound comprises one intractability group.
 66. The composition of claim 61, wherein the compound comprises two intractability groups.
 67. The composition of claim 61, wherein the compound comprises three or more intractability groups.
 68. The composition of claim 61, wherein the compound's molecular weight is about 2,000 or less.
 69. The composition of claim 61, wherein the compound's molecular weight is about 400 to about 2,000.
 70. The composition of claim 61, wherein the compound's molecular weight is about 2,000 to about 5,000.
 71. The composition of claim 61, wherein the hole transporting core comprises at least two aryl or heteroaryl rings.
 72. The composition of claim 61, wherein the hole transporting core comprises at least three aryl or heteroaryl rings.
 73. The composition of claim 61, wherein the hole transport core comprises only carbocyclic rings.
 74. The composition of claim 61, wherein the hole transport core comprises at least one spiro moiety.
 75. The composition of claim 61, wherein the hole transport core comprises at least one thiophene moiety.
 76. The composition of claim 61, wherein the hole transport core comprises at least two thiophene moieties.
 77. The composition of claim 61, wherein the hole transport core comprises at least one benzodithiophene moiety.
 78. The composition of claim 61, wherein the hole transport core comprises at least one heteroarylmoiety comprising at least one nitrogen.
 79. The composition of claim 61, wherein the hole transport core comprises at least one heteroarylmoiety comprising at least two nitrogens.
 80. The composition of claim 61, wherein the hole transport core comprises at least one piperazine core.
 81. The composition of claim 61, wherein the hole transport core comprises at least one pyrrole ring.
 82. The composition of claim 61, wherein the hole transport core comprises at least two pyrrole rings.
 83. The composition of claim 61, wherein the hole transport core comprises at least one silole ring.
 84. The composition of claim 61, wherein the hole transport core comprises at least two silole rings.
 85. The composition of claim 61, wherein the hole transport core comprises at least three fused rings.
 86. The composition of claim 61, wherein the hole transport core comprises at least five fused rings.
 87. The composition of claim 61, wherein the hole transport core is functionalized with at least one solubilizing group.
 88. The composition of claim 61, wherein the hole transport core is functionalized with at least two solubilizing groups.
 89. The composition of claim 61, wherein the hole transport core is functionalized with at least one solubilizing group which has a least four carbon atoms.
 90. The composition of claim 61, wherein the hole transport core is functionalized with at least one solublizing group which as an alkylene group comprising at least four carbon atoms.
 91. The composition of claim 61, wherein the first and second arylamine group are the same arylamine group.
 92. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein R1 and R2 are optionally substituted aryl or heteroaryl groups which may be the same or different.
 93. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein at least one of R1 and R2 is an optionally substituted phenyl group.
 94. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein at least one of R1 and R2 is an optionally substituted biphenyl group.
 95. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein at least one of R1 and R2 is an optionally substituted carbazole group.
 96. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein —N(R1)(R2) form an optionally substituted carbazole group.
 97. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein at least one of R1 and R2 is an optionally substituted naphthyl group.
 98. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein at least one of R1 and R2 is an optionally substituted thienobenzene group.
 99. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein at least one of R1 and R2 is an optionally substituted fluorene group.
 100. The composition of claim 61, wherein each of the first and second arylamine groups are independently represented by —N(R1)(R2), wherein at least one of R1 and R2 is an optionally substituted group comprising at least two fused aromatic rings.
 101. The composition of claim 61, wherein the intractability group comprises a crosslinking group.
 102. The composition of claim 61, wherein the intractability group comprises a non-crosslinking group.
 103. The composition of claim 61, wherein the intractability group comprises at least one ethylenically unsaturated moiety.
 104. The composition of claim 61, wherein the intractability group comprises a vinyl group.
 105. The composition of claim 61, wherein the intractability group comprises a benzocyclobutane group.
 106. The composition of claim 61, wherein the intractability group comprises an indenyl group.
 107. The composition of claim 61, wherein the intractability group comprises a a quaternary ammonium group.
 108. The composition of claim 61, wherein the intractability group comprises a a quaternary ammonium group comprising a tetraarylborate anion.
 109. The composition of claim 61, wherein the intractability group comprises a a quaternary ammonium group comprising a pentafluorophenylborate anion.
 110. The composition of claim 61, wherein the compound has a glass transition temperature of about 200° C. or less.
 111. The composition of claim 61, wherein the compound is a first compound, and the composition further comprises at least one additional second compound, different from the first compound, which activates a polymerization reaction for the composition.
 112. The composition of claim 61, wherein the compound is a first compound, and the composition further comprises at least one additional second compound, different from the first compound, which comprises para-styrene units.
 113. The composition of claim 61, wherein the compound is a first compound, and the composition further comprises at least one additional second arylamine compound, different from the first arylamine compound, wherein the second arylamine compound has only one crosslinking group.
 114. The composition of claim 61, wherein the compound is a first compound, and the composition further comprises at least one second arylamine compound, different from the first arylamine compound, wherein the second arylamine compound has three or more crosslinking groups.
 115. The composition of claim 61, wherein the compound is a first compound, and the composition further comprises at least one second arylamine compound, wherein the second arylamine compound has a lower LUMO and lower or similar HOMO compared to the first and compound.
 116. A composition comprising: at least one first compound and at least one second compound different from the first, wherein the at least one first compound comprises a hole transporting core which is a fluorene core or a biphenyl core, wherein the hole transporting core is covalently bonded to a first arylamine group and also covalently bonded to a second arylamine group, and wherein the core is further covalently bonded to at least two solubilizing groups comprising at least four carbon atoms, and wherein the solubilizing groups are optionally substituted with intractability groups; wherein the at least one second compound comprises a hole transporting core which is a fluorene core or a biphenyl core, wherein the hole transporting core is covalently bonded to a first arylamine group and also covalently bonded to a second arylamine group, wherein the second compound further comprises at least one intractability group which may be bonded to the first arylamine group, the second arylamine group, or both; wherein the first and second compounds have molecular weight of about 5,000 g/mole or less.
 117. The composition of claim 116, wherein the hole transporting core is a biphenyl core. 